Process for treating monazite acid leach residue

Abstract

The application relates to a processing method of monazite acid-dissolved slag, which comprises the following steps: mixing monazite acid-dissolved slag and water, then performing separation, mixing acid-dissolved slag light mud obtained through the separation with a hydrochloric acid solution and a reducing agent, performing acid dissolution, then performing first solid-liquid separation, and obtaining first filtrate; the mass concentration of the hydrochloric acid solution is 15%-25%, the volume of the hydrochloric acid solution is 3m 3 / 1000kg-5m 3 / 1000kg, the mass of the acid-dissolved slag light mud is 1000kg; the first filtrate is mixed with an oxidizing agent to perform oxidation reaction, then the obtained oxidation reaction liquid is mixed with a phosphorus source to perform first precipitation treatment, then second solid-liquid separation is performed, and iron precipitate and second filtrate are obtained; a first pH regulator is used to adjust the pH value of the second filtrate to 3.8-4.2, then hydrogen peroxide is added to perform second precipitation treatment, then third solid-liquid separation is performed, and thorium-uranium precipitate and third filtrate are obtained; the third filtrate is mixed with a rare earth precipitating agent to perform third precipitation treatment, and rare earth precipitate is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth extraction, in particular to a processing method of monazite acid leaching residue. BACKGROUND

[0002] With the development of mineral processing technology, monazite gradually becomes an important phosphate rare earth ore, which is mainly derived from the mineral processing by-products of zirconium-titanium ore, often accompanied by rutile, ilmenite, zircon and a small amount of radioactive elements thorium and uranium. The commonly used decomposition methods in industry mainly include acid roasting method and alkali roasting decomposition method, and the most widely used method is alkali roasting decomposition method. After monazite is roasted by sodium hydroxide, sodium carbonate and the like, rare earth, thorium and uranium form oxides that are soluble in hydrochloric acid, while the undecomposed ilmenite, zircon, monazite and monazite ore and the like are insoluble in acid. In the preparation of chlorinated rare earth by hydrochloric acid dissolution, iron, aluminum, thorium and uranium enter the precipitate residue together with the acid-insoluble substance, which is called monazite acid leaching residue. The main components of monazite acid leaching residue include iron, silicon, titanium, rare earth, zirconium, aluminum, barium, thorium, uranium and the like, among which the content of rare earth is generally 5% to 15%, and some even higher than 15%; the content of thorium is generally 2% to 5%, and some even higher than 5%. Rare earth, thorium and uranium are important strategic resources, and monazite acid leaching residue needs to be comprehensively recycled and utilized. At present, there are few reports on the comprehensive recovery and utilization of rare earth, iron and thorium uranium in monazite acid leaching residue. SUMMARY

[0003] Based on this, the present application provides a processing method of monazite acid leaching residue which can extract rare earth, thorium uranium and iron elements.

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

[0005] In one aspect, the present application provides a processing method of monazite acid leaching residue, comprising the following steps:

[0006] After mixing the monazite acid leaching residue and water, sorting is performed to obtain acid leaching residue light mud;

[0007] After mixing the acid leaching residue light mud, hydrochloric acid solution and reducing agent for acid leaching, first solid-liquid separation is performed to obtain first filtrate; the mass concentration of the hydrochloric acid solution is 15% to 25%, and the volume of the hydrochloric acid solution to the mass of the acid leaching residue light mud is 3 m 3 / 1000 kg to 5 m 3 / 1000 kg;

[0008] The first filtrate is mixed with an oxidizing agent to perform oxidation reaction to obtain an oxidation reaction liquid;

[0009] After mixing the oxidation reaction liquid and a phosphorus source for first precipitation treatment, second solid-liquid separation is performed to obtain iron precipitate and second filtrate, respectively.

[0010] The pH value of the second filtrate is adjusted to 3.8-4.2 by using a first pH regulator, and then hydrogen peroxide is added for a second precipitation treatment, and after a third solid-liquid separation, a thorium-uranium precipitate and a third filtrate are obtained respectively;

[0011] The third filtrate is mixed with a rare earth precipitant for a third precipitation treatment to obtain a rare earth precipitate.

[0012] In some embodiments of the method for treating the acid-leached residue of xenotime, the mass concentration of the hydrochloric acid solution is 15%-20%.

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

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

[0015] In the first precipitation treatment step, a step of adjusting the pH value of the first precipitation liquid of the oxidation reaction solution and the phosphorus source to 1.5-2.5 by using a second pH regulator is further included; optionally, the pH value of the first precipitation liquid is adjusted to 1.5-2.

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

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

[0018] In some embodiments of the method for treating the acid-leached residue of xenotime, the oxidizing agent includes at least one of hydrogen peroxide, sodium chlorate, sodium hypochlorite, oxygen and ozone.

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

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

[0021] In some embodiments of the method for treating the monazite acid leaching residue, the rare earth precipitant comprises at least one of ammonium bicarbonate, ammonium carbonate, sodium carbonate, sodium bicarbonate, ammonia water and sodium hydroxide.

[0022] In some embodiments of the method for treating the monazite acid leaching residue, the step of mixing the third filtrate and the rare earth precipitant further comprises the step of adding a crystal form of rare earth; and / or

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

[0024] In some embodiments of the method for treating the monazite acid leaching residue, before the first solid-liquid separation step, the method further comprises the step of adjusting the pH value of the acid leaching solution to 1.0-1.5 by using a third pH adjuster.

[0025] Compared with the prior art, the method for treating the monazite acid leaching residue has the following beneficial effects:

[0026] The method for treating the monazite acid leaching residue of the present application first mixes the monazite acid leaching residue and water and performs sorting to separate the acid leaching residue light mud and heavy sand, then performs acid leaching on the acid leaching residue light mud 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 leaching step and the ratio between the acid leaching residue light mud and the hydrochloric acid solution, the rare earth, thorium, uranium and iron elements in the acid leaching residue light mud react with the hydrochloric acid to generate chloride salts, which is conducive 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 leaching residue, and is conducive to the subsequent recovery of the rare earth; the first filtrate is mixed with an oxidizing agent to perform an oxidation reaction, so that the divalent iron is oxidized into trivalent iron, and the trivalent iron generates iron precipitates with a phosphorus source, 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 generate thorium precipitates, the uranium in the second filtrate reacts with the hydrogen peroxide to generate uranium precipitates, and the thorium precipitates and the uranium precipitates have a small amount of iron impurities; the third filtrate is mixed with a rare earth precipitant to perform a third precipitation treatment, thereby obtaining rare earth precipitates and recovering the rare earth element, and the recovery rate of the rare earth element is high.

[0027] The method for treating the monazite acid leaching residue of the present application has a simple process, simple equipment investment and convenient operation. No ion exchange column or extraction tank is needed, and a conventional stirring tank can be used. DETAILED DESCRIPTION

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

[0029] It should also be understood that the application can be implemented in many different forms and is not limited to the embodiments and examples described herein, which can be modified in a variety of ways without departing from the spirit of the application. For example, features described or illustrated as part of one embodiment can be used with another embodiment to yield still a further embodiment. Additionally, the description of the application given herein is not intended to limit the scope of the application but rather serve as an example of how the application can be implemented.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing the embodiments and examples only and is not intended to be limiting of the application.

[0031] Unless otherwise indicated, or unless the context clearly indicates otherwise, the terms or phrases used in this application have the following meanings:

[0032] In this application, the terms "plurality", "a plurality of", "plurality of times" and the like, unless otherwise specified or limited in context, refer to more than two or equal to two. For example, "one or more" means one or more than two.

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

[0034] As used herein, "suitable combinations", "suitable manner", "any suitable manner" and the like mean that the technical solutions of the application can be implemented, the technical problems of the application can be solved, and the intended technical effects of the application can be achieved.

[0035] As used herein, "preferably", "more preferably", "even more preferably", "suitably" and the like are used to describe embodiments or examples that are better than others, and it should be understood that they do not constitute a limitation on the scope of protection of the application. If there are multiple "preferably" in a technical solution, and there is no special description, and there is no contradictory relationship or mutual restriction, each "preferably" is independent.

[0036] In this application, "further", "more further", "particularly" and the like are used for description purposes, indicating differences in content, but should not be understood as limiting the scope of protection of the application.

[0037] In the present application, "optionally", "optional", "option" means optional, that is, selected from "yes" or "no" two parallel schemes. If there are multiple "options" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "option" is independent.

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

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

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

[0041] In the present application, unless otherwise specified, the temperature parameter allows for constant temperature treatment and allows for variation within a certain temperature interval. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. It is allowed to fluctuate within the range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C.

[0042] In the present 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 the present application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of the present application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0043] In the present application, if the unit is only behind the right end point, it means that the units of the left end point and the right end point are the same. For example, 3~5 h means that the units of the left end point "3" and the right end point "5" are both h (hour).

[0044] All the documents mentioned in the present application are incorporated by reference in the present application as if each document is incorporated by reference individually. Unless and to the extent that the purpose and / or technical solution of the present application is conflicted, the documents mentioned in the present application are incorporated by reference in the present application in the whole content and purpose. When the present application refers to the documents, the definitions of the related technical features, terms, names, phrases, etc. in the documents are also incorporated by reference. When the present application refers to the documents, the examples and preferred modes of the related technical features are also incorporated by reference in the present application as far as the present application can be implemented. It should be understood that when the content of the reference is conflicted with the description in the present application, the present application is correct or is amended according to the description in the present application adaptively.

[0045] The mass or weight of the related components mentioned in the present application embodiment specification can not only refer to the specific content of each component, but also represent the proportional relationship between the mass or weight of each component. Therefore, as long as the content of the related components in the present application embodiment specification is enlarged or reduced in proportion, it is within the scope disclosed in the present application embodiment specification. Specifically, the mass or weight mentioned in the present application embodiment specification can be μg, mg, g, kg and other units well known in the chemical field.

[0046] Although xenotime and monazite are both phosphate rare earth ores, they have certain differences in composition and phase, and the processing technology and the acid-soluble residue obtained are different. If the existing monazite acid-soluble residue method is used to process xenotime acid-soluble residue, there are problems of low rare earth leaching rate, high processing cost, or ineffective recovery of thorium, iron and other elements.

[0047] An embodiment of the present application provides a processing method of xenotime acid-soluble residue, comprising the following steps:

[0048] Step S10: After mixing the xenotime acid-soluble residue and water, sorting is performed to obtain acid-soluble residue light mud.

[0049] It can be understood that the heavy sand is mostly un-decomposed xenotime, monazite, zirconium iron ore and the like, which is difficult to dissolve in acid and needs to be sorted out and returned to alkali roasting. If necessary, the sorted heavy sand also needs to be further mineralized and enriched in rare earth and then returned to alkali roasting. Before acid-soluble, the xenotime acid-soluble residue is mixed with water and sorted to separate the acid-soluble residue light mud from the heavy sand. The thorium, uranium and rare earth of the light mud are recovered and utilized, which can reduce the residue amount, improve the recovery rate of rare earth and effectively avoid the material consumption and yield loss caused by the heavy sand when valuable elements are extracted from the xenotime acid-soluble residue.

[0050] In some examples, the solid content of the water-soluble residue solution obtained by mixing the monazite acid-soluble residue and water in step S10 is 20% to 30%.

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

[0052] The monazite acid-soluble residue and water are mixed and stirred for 2 to 4 hours, and after the stirring is stopped, the upper light slurry is collected and subjected to solid-liquid separation to obtain the acid-soluble residue light mud.

[0053] Further, the step of collecting the upper light slurry comprises pumping the upper light slurry into a filter press for pressure filtration, or opening a middle valve to allow the upper light slurry to flow into a collection barrel, and then performing solid-liquid separation, and the solid phase is the acid-soluble residue light mud. It can be understood that the liquid phase can be returned to the monazite acid-soluble process or recycled in the process.

[0054] It can be understood that the slurry with a larger specific gravity (heavy sand) in the lower layer is subjected to subsequent beneficiation treatment.

[0055] It can be understood that before step S20, there is also a step of analyzing the element content in the acid-soluble residue light mud obtained in step S10.

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

[0057] The acid-soluble residue light mud is subjected to acid-soluble treatment under the action of the hydrochloric acid solution and the 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 residue light mud and the hydrochloric acid solution, the rare earth elements, thorium, uranium, and iron elements in the acid-soluble residue light mud react with hydrochloric acid to generate chloride salts, which is conducive to improving the leaching rate of the rare earth elements, thorium, uranium, and iron elements, and especially effectively improving the leaching rate of the insoluble terbium and cerium in the acid-soluble residue.

[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 can be 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 volume-to-mass ratio of the hydrochloric acid solution to the acid-soluble residue 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, 4.5 m 3 / 1000 kg, 4.8 m 3 / 1000 kg, 5 m 3 / 1000 kg; in some examples, it can be within the range constituted by any two of these point values as end values, and the same applies 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 of the examples, in step S20, the volume-to-mass ratio of the hydrochloric acid solution to the acid-soluble residue light mud is 3 m 3 / 1000 kg to 4 m 3 / 1000 kg.

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

[0066] It can be understood that the mass ratio of the rare earth oxides to the reducing agent in the acid-soluble residue 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, 1:0.3.

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

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

[0069] In some examples, the reducing agent in step S20 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 examples, in step S20, the acid-dissolved residue and the hydrochloric acid solution are mixed and stirred for 2-4 hours, heated to 50-60°C, then the reducing agent is added, and the temperature is continuously increased to ≥95°C, and the acid-dissolved solution is kept for 1-2 hours.

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

[0072] It can be understood that, before the first solid-liquid separation step, the pH value of the acid-dissolved solution is adjusted to 1.0-1.5, which reduces the acidity of the acid-dissolved solution and reduces 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, and sodium hydroxide.

[0074] In some examples, in step S20, when the temperature of the acid-dissolved solution is reduced to ≤80°C, the third pH adjuster is added.

[0075] The first filtrate and the oxidizing agent are mixed to perform an oxidation reaction, so that the divalent iron is oxidized to trivalent iron. It can be understood that, in the first solid-liquid separation, the first filtrate is obtained, and a first solid phase is also obtained. The filter residue is washed by cross-flow stirring with water, and solid-liquid separation is performed. The washing water is returned to step S20 to prepare hydrochloric acid, and the filter residue enters the beneficiation.

[0076] Step S30: The first filtrate obtained in step S20 and an oxidizing agent are mixed to perform an oxidation reaction, to obtain an oxidation reaction liquid.

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

[0078] It can be understood that the amount of the oxidizing agent used can be determined according to whether the divalent iron in the first filtrate is completely converted into trivalent iron, or the concentration of Fe 2+ in the solution is less than 0.01 g / L.

[0079] Step S40: After the oxidation reaction liquid obtained in step S30 and a phosphorus source are mixed to perform 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 and the oxidizing agent are mixed to perform an oxidation reaction, so that the divalent iron is oxidized into trivalent iron, and the trivalent iron reacts with the phosphorus source to form an iron precipitate, thereby recovering the iron element.

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

[0082] It can be understood that the monohydrogen phosphate includes but is not limited to sodium monohydrogen phosphate, and the dihydrogen phosphate includes but is not limited to sodium dihydrogen phosphate. Alternatively, the phosphorus source is phosphoric acid.

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

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

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

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

[0087] Adjusting the pH value of the first precipitation liquid to a specific range is beneficial to the formation of the iron precipitate and less loss of rare earth elements. It can be understood that adjusting 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 examples, the pH value of the first precipitation liquid is adjusted to 1.5-2 in step S40.

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

[0090] In some examples, the temperature of the first precipitation liquid is increased to above 90°C before the pH value of the first precipitation liquid is adjusted by using the second pH adjuster in step S40.

[0091] Step S50: adjusting the pH value of the second filtrate obtained in step S40 to 3.8-4.2 by using a first pH regulator, and then adding hydrogen peroxide to perform a second precipitation treatment, and then 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, and under this pH condition, the thorium element reacts with the first pH regulator to form a thorium precipitate, the tetravalent uranium forms a uranium hydroxide precipitate, and the hexavalent uranium in the second filtrate reacts with the hydrogen peroxide to form a uranium precipitate, thereby avoiding the problem that the high-valent uranyl is difficult to precipitate under this pH condition, and the thorium precipitate and the uranium precipitate have fewer impurities, and the obtained thorium-uranium precipitate has a higher grade; at the same time, the rare earth elements do 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 can be understood that the pH value of the second filtrate is adjusted to, but not limited to, 3.8, 3.9, 4.0, 4.1, and 4.2.

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

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

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

[0102] It can be 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, 1:5.

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

[0104] Step S60: mixing the third filtrate obtained in step S50 and a rare earth precipitant to perform a third precipitation treatment to obtain a rare earth precipitate.

[0105] The processing method of the xenotime acid leaching residue provided in the present application first mixes the xenotime acid leaching residue and water and performs sorting to separate the acid leaching residue light mud from the heavy sand, then performs acid leaching on the acid leaching residue light mud 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 leaching step and the ratio between the acid leaching residue light mud and the hydrochloric acid solution, the rare earth elements, thorium elements, uranium elements and iron elements in the acid leaching residue light mud react with the hydrochloric acid to generate chloride salts, which is conducive to improving the leaching rate of the rare earth elements, thorium elements, uranium elements and iron elements, and especially effectively improves the leaching rate of the insoluble terbium and cerium in the acid leaching residue; mixing the first filtrate and an oxidizing agent to perform an oxidation reaction to oxidize the divalent iron into trivalent iron, and the trivalent iron reacts with a phosphorus source to generate an iron precipitate, thereby recovering the iron elements; adjusting the pH value of the second filtrate to a specific value, under the pH condition, the thorium elements react with a first pH adjuster to generate a thorium precipitate, the uranium in the second filtrate reacts with hydrogen peroxide to generate a uranium precipitate, and the thorium precipitate and the uranium precipitate have a small amount of iron impurities; then mixing the third filtrate and a rare earth precipitant to perform a third precipitation treatment to obtain a rare earth precipitate, thereby recovering the rare earth elements.

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

[0107] 2RE 3+ +3 CO3 2- →RE2(CO3)3↓.

[0108] In some 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 examples, in step S60, the molar ratio of the rare earth elements in the third filtrate to the rare earth precipitant is 1:(2.1~2.8).

[0110] It can be understood that the molar ratio of the rare earth elements in the third filtrate to the rare earth precipitant 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, 1:2.8.

[0111] In some examples, the pH value of the third precipitation treatment in step S60 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 examples, in step S60, the third precipitation treatment is performed by first adding the crystal rare earth into the third filtrate, and then adding the rare earth precipitator.

[0114] It can be understood that step S60 further includes a step of performing solid-liquid separation on the slurry after the third precipitation treatment, the liquid phase flows into a storage tank, ammonium chloride is recovered by evaporation and concentration crystallization, and distilled condensate is reused without wastewater discharge; the solid phase is subjected to cross-flow water washing, and then solid-liquid separation is performed to obtain the rare earth precipitator, and the washing liquid can be used for preparing the ammonium bicarbonate or sodium carbonate solution in the ammonium carbonate precipitation.

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

[0116] The processing method of the xenotime acid-soluble residue of the present application is simple in process, simple in equipment investment, and convenient to operate. Ion exchange columns or extraction tanks are not required, and a conventional stirring tank can be used, which is friendly to the working environment. The wastewater is concentrated by a membrane and then evaporated and concentrated for recycling, the evaporation waste heat is used for the sulfuric acid slurry reaction, and the waste residue is treated by a sludge drying system, which can realize residue reduction, resource utilization, and harm reduction. This process fundamentally solves the problems of pollution, resource waste, and large consumption of raw and auxiliary materials caused by the rare earth smelting process, and realizes green and efficient rare earth and co-associated resources.

[0117] The raw materials used in the present application are commercially available and do not have special requirements. The xenotime acid-soluble residue is well known to those skilled in the art and does not have special requirements.

[0118] The present application will be further described in detail below in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0119] Example 1

[0120] S1: Xenotime acid-soluble residue sorting

[0121] 2000 kg of xenotime acid-soluble residue was placed in a 10 m 3The acid-resistant rubber-lined iron mixing tank with conical bottom and straight cylinder type is added with sludge washing recycled water for slurry, with solid content of 30%, and is stirred for 2 hours. After stopping stirring, it is clarified for 1 hour. The upper light slurry is pumped into a filter press for pressure filtration. The filter cake, i.e. acid-soluble sludge light mud, is sent to S2. The filtrate is stored in a storage tank for recycling.

[0122] The acid-soluble sludge light mud obtained after gravity separation has a water content of about 46.90%. The main chemical components of the dry basis are shown in Table 1.

[0123] Table 1

[0124]

[0125] S2: acid dissolution

[0126] In the PPH mixing tank, 3m 3 of hydrochloric acid with a mass concentration of 15% prepared by circulating water and industrial hydrochloric acid is added to 1000 kg of acid-soluble sludge light mud obtained in S1, and is stirred for 2 hours. Then, the temperature is increased to 50℃. Thiourea is added according to the molar ratio of REO in light mud to reducing agent of 1:0.125. The temperature is continuously increased to above 95℃, and is kept for 1 hour. After stopping heating, when the temperature is below 80℃, ammonium bicarbonate is added to adjust the pH to 1.5. Solid-liquid separation is performed by a filter press. The first filtrate 2.98m 3 enters S3. The filter residue is washed with 1.25m 3 of water by stirring, and is subjected to solid-liquid separation by a diaphragm filter press. The washing filtrate enters a storage tank and is reserved for preparation of dilute hydrochloric acid in the next S2. The filtrate 1.2m 3 , in which the REO content is 4.13g / L, is used as washing water. The filter residue enters the mineral processing process. The contents of iron, phosphorus, rare earth, thorium and uranium in the first filtrate are shown in Table 2.

[0127] Table 2

[0128]

[0129] S3: iron recovery

[0130] The 2.98m 3 of the first filtrate obtained by filter pressing in S2 is pumped into a 10m 2+Afterwards, 112 kg of 85% commercial phosphoric acid is added at a P:Fe molar ratio of 1:1, the temperature is raised to above 90°C, ammonium bicarbonate is added to adjust the pH to 1.5, a precipitate is formed, after stirring for 1 hour, a sample is analyzed and the solution contains 0.2 g / L of iron ions, after 2 hours of aging, solid-liquid separation is performed using a filter press, the filter residue is the iron phosphate product, and the second filtrate is passed to S4.

[0131] S4: Recovery of thorium-uranium

[0132] The second filtrate is at a temperature of 55°C, while hot, ammonium bicarbonate is slowly added, the pH is adjusted to 4.0, hydrogen peroxide is added (the molar ratio of uranium in the second filtrate to hydrogen peroxide is 1:2), stirring is performed for 2 hours, 2 hours of aging is performed, and solid-liquid separation is performed using a filter press to obtain a third filtrate and a thorium-uranium-containing filter cake, the filter cake is unloaded from the filter press into a bag and sent to a thorium-uranium separation and purification process; the third filtrate is passed to S5.

[0133] S5: Precipitation of rare earths

[0134] The third filtrate obtained in S4 is at a temperature of about 45°C, 5 kg of the crystalline rare earth carbonate previously prepared is added first, then ammonium bicarbonate solution is slowly added, the precipitation endpoint is controlled at a pH of 7.2, the solution is tested and contains less than 0.001 g / L of REO, the addition of ammonium bicarbonate solution is stopped, the molar ratio of REO to ammonium bicarbonate is 1:2.8, stirring is continued for 1 hour, 2 hours of clarification is performed, and solid-liquid separation is performed using a filter press to obtain a filter cake and a filtrate, the filtrate is the precipitation mother liquor and is passed to S7 for treatment, and the filter cake is rare earth carbonate and is passed to S6 for washing.

[0135] S6: Washing of rare earth carbonate

[0136] The filter cake obtained by filtration in S5 is subjected to two cross-flow water washes, solid-liquid separation is performed using a filter press each time, the washed rare earth carbonate is bagged, and the filtrate is used to prepare ammonium bicarbonate solution.

[0137] S7: Treatment of the precipitation mother liquor

[0138] The filtrate obtained by filtration of the rare earth precipitate in S5 is passed to a storage tank, after treatment using a membrane, part of the water is returned to wash the rare earth carbonate, the concentrated water is used to recover ammonium chloride by means of two-effect evaporation, and the distilled condensate is reused, with no wastewater being discharged.

[0139] Example 2

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

[0141] Example 3

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

[0143] Example 4

[0144] The same as example 1, except that the molar ratio of REO: reducing agent in the light mud in the S2 acid leaching step is 1:0.03.

[0145] Example 5

[0146] The same as example 1, except that the molar ratio of REO: reducing agent in the light mud in the S2 acid leaching step is 1:0.3.

[0147] The rare earth leaching rate is basically the same as example 1, the cost is increased compared with example 1, and the environmental impact is increased.

[0148] Example 6

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

[0150] Example 7

[0151] The same as example 1, except that the reducing agent thiourea is replaced by hydrazine hydrate in the S2 acid leaching step, 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 the amount of 15% hydrochloric acid used in the S2 acid leaching step is 5m 3 .

[0154] Example 8 has more materials consumed in the excess acid neutralization, resulting in higher salt content.

[0155] Example 9

[0156] The same as example 1, except that the mass concentration of hydrochloric acid in the S2 acid leaching step is 20%.

[0157] Example 10

[0158] The same as example 1, except that the mass concentration of hydrochloric acid in the S2 acid leaching step is 25%.

[0159] Example 11

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

[0161] Example 12

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

[0163] Example 13

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

[0165] Example 14

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

[0167] Example 15

[0168] The same as example 1, except that the monazite acid leaching residue is different, and the acid leaching residue light mud obtained in the S1 step in example 1 has a water content of about 51.24%, and the main chemical components of the dry basis are shown in Table 3.

[0169] Table 3

[0170]

[0171] Example 16

[0172] The same as example 1, except that the monazite acid leaching residue is different, and the main components of the acid leaching residue light mud obtained in the S1 step in example 1 are as follows: the wet basis analysis has a water content of about 52.56%, and the 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 S2 acid leaching step, the amount of 15% hydrochloric acid used is 2m 3 .

[0177] Comparative Example 2

[0178] The same as example 1, except that in the S2 acid leaching step, the mass concentration of hydrochloric acid is 10%.

[0179] The treatment parameters of the monazite acid leaching residue in each example and comparative example are shown in Table 5, wherein:

[0180] "Light mud: hydrochloric acid" refers to the mass ratio of the acid-soluble residue light mud to the volume of the hydrochloric acid solution; "REO: reducing agent" refers to the mass ratio of the rare earth oxides in the acid-soluble residue light mud to the reducing agent; "Terbium content" refers to the content of rare earth terbium in the S2 first filtrate and the change in the content of rare earth terbium in the S1 acid-soluble residue light mud; "pH in S3" refers to the pH value of the precipitation end point control in the S3 step; "Uranium: hydrogen peroxide" refers to the molar ratio of uranium in the second filtrate to hydrogen peroxide; "pH in S5" refers to the pH value of the precipitation end point control in the S5 step.

[0181] Table 5

[0182]

[0183] The recovery rates of the elements are shown in Table 6, wherein:

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

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

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

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

[0188] Table 6

[0189]

[0190] It can be seen that, compared with the comparative examples, the treatment method of the xenotime acid-soluble residue provided by each of the examples has a higher recovery rate of rare earth, thorium-uranium and iron elements. Among them, the rare earth content in the xenotime acid-soluble residue 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-soluble residue used in Example 16 is higher than that in Example 1, and the rare earth leaching rate is slightly improved.

[0191] Each technical feature of the above-described examples can be combined arbitrarily, and in order to make the description concise, not all possible combinations of each technical feature in the above-described examples are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0192] The above-described embodiments only express several implementation manners of the present application, facilitate specific and detailed understanding of the technical solutions of the present application, but cannot be understood as a limitation on the patent protection scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications 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. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments by the skilled person in the art all belong to the protection scope of the appended claims of the present application. Therefore, the patent protection scope of the present application should be subject to the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method for treating acid-soluble slag from yttrium phosphate rock, characterized in that, Includes the following steps: After mixing the acid-soluble slag from yttrium phosphate ore with water, the mixture is sorted to obtain acid-soluble sludge. The acid-dissolved sludge, hydrochloric acid solution, and reducing agent are mixed and acid-dissolved, followed by a first solid-liquid separation to obtain a first filtrate. The hydrochloric acid solution has a mass concentration of 15% to 25%, and the volume ratio of the hydrochloric acid solution to the mass ratio of the acid-dissolved sludge is 3 m³. 3 / 1000 kg ~5 m 3 / 1000 kg; The first filtrate and the oxidant are mixed to carry out an oxidation reaction, resulting in an oxidation reaction solution; After mixing the oxidation reaction solution and the phosphorus source for a first precipitation treatment, a second solid-liquid separation is performed to obtain iron precipitate and second filtrate, respectively. The pH of the second filtrate was adjusted to 3.8-4.2 using a first pH adjuster, and then hydrogen peroxide was added for a second precipitation treatment. After a third solid-liquid separation, thorium uranium precipitate and third filtrate were obtained respectively. The third filtrate and rare earth precipitant are mixed for a third precipitation treatment to obtain rare earth precipitate.

2. The method for treating acid-soluble slag from yttrium phosphate rock as described in claim 1, characterized in that, The mass concentration of the hydrochloric acid solution is 15%~20%.

3. The method for treating acid-soluble slag from yttrium phosphate rock as described in claim 1, characterized in that, The mass ratio of rare earth oxides in the acid-soluble sludge to the reducing agent is 1:(0.02~0.3).

4. The method for treating yttrium phosphate slag as described in claim 3, characterized in that, The mass ratio of rare earth oxides in the acid-soluble sludge to the reducing agent is 1:(0.05~0.3).

5. The method for treating acid-soluble slag from yttrium phosphate rock as described in claim 1, characterized in that, The molar ratio of the phosphorus source to the ferric iron in the oxidation reaction solution is 0.9~1:1; and / or The first precipitation treatment step further includes adjusting the pH of the oxidation reaction solution and the first precipitation solution of the phosphorus source to 1.5~2.5 using a second pH adjuster.

6. The method for treating acid-soluble slag from yttrium phosphate rock as described in claim 5, characterized in that, Adjust the pH of the first precipitate to 1.5-2.

7. The method for treating acid-soluble slag from yttrium phosphate rock as described in 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).

8. The method for treating yttrium phosphate slag as described in any one of claims 1 to 7, characterized in that, The reducing agent includes at least one of thiourea, sodium sulfite, sodium bisulfite, hydrazine hydrate, and formaldehyde.

9. The method for treating acid-soluble slag from yttrium phosphate rock as described in any one of claims 1 to 7, characterized in that, The oxidant includes 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.

10. The method for treating yttrium phosphate slag as described in any one of claims 1 to 7, characterized in that, The first pH adjuster includes at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia, and sodium hydroxide; and / or The rare earth precipitant includes at least one of ammonium bicarbonate, ammonium carbonate, sodium carbonate, sodium bicarbonate, ammonia, and sodium hydroxide.

11. The method for treating acid-soluble slag from yttrium phosphate rock as described in any one of claims 1 to 7, characterized in that, The step of mixing the third filtrate and the rare earth precipitant also includes the step of adding crystalline rare earth elements; and / or The pH value of the third precipitation treatment is 6.8~7.

2.

12. The method for treating acid-soluble slag from yttrium phosphate rock as described in any one of claims 1 to 7, characterized in that, Before performing the first solid-liquid separation step, the method further includes a step of adjusting the pH value of the acid solution after acid dissolution to 1.0~1.5 using a third pH adjuster.

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