A method for preparing low-sulfate rare earth carbonate using a mixed precipitant

Abstract

The application provides a method for preparing low-sulfate rare earth carbonate by using a mixed precipitant, and belongs to the technical field of hydrometallurgy. The method provided by the application is characterized in that, after the rare earth sulfate solution and the mixed precipitant solution are added in a parallel flow mode, a heat preservation reaction is performed. The method uses the mixed precipitant for precipitation, improves the alkalinity of the precipitant, and effectively reduces carbon emission and wastewater volume in the precipitation process. The method solves the problem of high sulfate impurity in the process of transforming chlorinated rare earth by using the mixed rare earth sulfate solution and the ammonium bicarbonate precipitation method, and solves the problem of high cost of using relevant organic extractants in the process of transforming by using the extraction method. The rare earth carbonate obtained by the method has a REO content of 50% to 65% and a sulfate content of less than 0.01%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrometallurgy, in particular to a method for preparing low-sulfate carbonates of rare earths using a mixed precipitant. BACKGROUND

[0002] The decomposition of rare earth concentrates is mostly carried out by high-temperature roasting with concentrated sulfuric acid. After high-temperature roasting, a mixed rare earth sulfate solution is obtained. The roasted ore is subjected to a water leaching impurity removal process to obtain a rare earth sulfate water leaching solution, which is then subjected to ammonium salt transformation to obtain mixed rare earth carbonates. However, the mixed rare earth carbonates obtained by precipitation in a sulfuric acid system contain a relatively high SO4 2- Therefore, the impurity SO4 2- in the chlorinated rare earth solution obtained after dissolution of concentrated hydrochloric acid is relatively high.

[0003] Patent No. CN111020240A describes a method and device for continuously preparing a mixed chlorinated rare earth solution from a rare earth sulfate solution. The invention involves a special device that can achieve continuous production of a mixed chlorinated rare earth solution from a rare earth sulfate water leaching solution, continuous precipitation of rare earth carbonates from a rare earth sulfate solution, and improved equipment utilization and automation of production. However, the content of SO4 2- in this process is not considered.

[0004] Patent No. CN101798627A describes a new method for precipitating rare earths, which uses pure magnesium bicarbonate and / or calcium bicarbonate aqueous solution prepared by calcination-digestion-carbonization of calcium or / and magnesium minerals as a precipitant. Although the use of magnesium bicarbonate reduces the cost of carbon precipitation, the content of SO4 2- in the carbonated rare earth sulfate is not considered. SUMMARY

[0005] In view of the above, the present application aims to provide a method for preparing low-sulfate carbonates of rare earths using a mixed precipitant. The method provided by the present application can significantly reduce the content of sulfate in the obtained carbonates of rare earths, making it <0.01%.

[0006] To achieve the above-mentioned purposes, the present application provides the following technical solutions:

[0007] One of the technical solutions of the present application is a method for preparing low-sulfate carbonates of rare earths using a mixed precipitant. The method uses a parallel flow method to add a rare earth sulfate solution and a mixed precipitant solution, and then performs a heat preservation reaction.

[0008] The second technical solution of the present application is a method for reducing the content of sulfate in a rare earth sulfate. The method uses the method described in the above technical solution to prepare low-sulfate carbonates of rare earths.

[0009] The present application discloses the following technical effects:

[0010] The application uses mixed precipitants to precipitate, improves the alkalinity of the precipitant, and effectively reduces carbon emissions and wastewater during the precipitation process.

[0011] The application solves the problem of high sulfate impurities in the process of transforming mixed rare earth sulfate solution into ammonium bicarbonate precipitation method of rare earth chloride, and solves the problem of high cost of using related organic extractants in the extraction method transformation process.

[0012] The raw materials used in the application have low cost and low energy consumption at room temperature, are simple to operate, and are easy to scale up for industrial production.

[0013] The product obtained by the application has high grade, facilitates product transportation, and reduces transportation costs. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, without creative labor, other drawings can also be obtained from these drawings.

[0015] Figure 1 SEM of low-sulfate rare earth carbonate prepared for Example 3 of the application. DETAILED DESCRIPTION

[0016] The detailed description of the various exemplary embodiments of the application should not be considered as limiting the application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the application.

[0017] It should be understood that the terms described in the application are only for describing the specific embodiments, and are not used to limit the application. In addition, for the numerical range in the application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the range, and any other stated value or intermediate value in the range is also included in the application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0018] 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 the application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of conflict between any incorporated document and the content of this specification, the content of this specification shall prevail.

[0019] Many modifications and variations of the specific embodiments of the application can be made without departing from the scope or spirit of the application, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0020] As used herein, the terms "comprise", "comprising", "include", "including", "have" and "having" and the like are open-ended, and specifically mean "including, but not limited to".

[0021] The application provides a method for preparing low-sulfate carbonates of rare earth elements using a mixed precipitant, in which the rare earth sulfate solution and the mixed precipitant solution are fed in a parallel flow mode, and then a heat preservation reaction is performed.

[0022] In the application, when the pH value of the reaction system is 5.2, the precipitation begins to be produced, and when the reactor is full, the product, the rare earth carbonate, is separated. In the process of separating the precipitate (i.e. the product, the sulfate carbonate of rare earth elements), the rare earth sulfate solution and the mixed precipitant solution are fed in a parallel flow mode, so that the continuous production is realized.

[0023] In some embodiments of the application, the rare earth sulfate solution and the mixed precipitant solution are fed in a parallel flow mode in the reactor for heat preservation reaction, and water is pre-added in the reactor as a bottom liquid. The application does not have special requirements for the reactor, and any reactor known to those skilled in the art can be selected.

[0024] In some embodiments of the application, the rare earth sulfate solution is a single rare earth sulfate solution or a mixed rare earth sulfate solution, and the concentration of the rare earth sulfate solution is 1-45 g / L in terms of REO.

[0025] In some embodiments of the application, the concentration of HCO3 - in the mixed precipitant solution is 0.43-1 mol / L, and the concentration of OH - in the mixed precipitant solution is 0.43-1 mol / L.

[0026] In the application, if the content of HCO3 - is too low, the volume of supernatant increases, and the amount of waste water increases, and if the content of HCO3 - is too high, the local reaction is too violent, and the amount of sulfate encapsulation increases. If the concentration of the mixed precipitant is too low, the amount of waste water increases, and if the concentration of the mixed precipitant is too high, the product produces rare earth hydroxide.

[0027] In some embodiments of the application, the mixed precipitant is two of ammonium bicarbonate, ammonia water, sodium bicarbonate, sodium hydroxide, ammonium carbonate and sodium carbonate, and the mixed precipitant contains HCO3 - and OH- .

[0028] In some embodiments of the present invention, the mixed precipitant is ammonium bicarbonate and ammonia, sodium bicarbonate and sodium hydroxide, ammonium bicarbonate and ammonium carbonate, or sodium bicarbonate and sodium carbonate.

[0029] In some embodiments of the present invention, the flow rate of the mixed precipitant solution is: the time for the feed liquid to fill the reaction vessel is greater than or equal to 2 hours and less than or equal to 8 hours, and the feed is kept at a uniform rate; the relative flow rate ratio of the rare earth sulfate solution to the mixed precipitant solution is 1:(2.8-3).

[0030] In this invention, the feed rate is controlled by adjusting the feeding time of each batch of material, maintaining a uniform feeding speed. In actual operation, during the first feeding, the liquid in the reactor is filled from empty to full, with the time to full control being greater than or equal to 2 hours and less than or equal to 8 hours, maintaining this uniform feeding speed. This uniform feeding speed is maintained throughout the subsequent continuous production process. If the flow rate is too fast, the reaction will be incomplete, resulting in smaller crystal particles that are difficult to filter; if the reaction is too slow, it will waste time. For economic reasons, the preferred flow rate of this invention is the parameters described above.

[0031] In this invention, if the flow rate ratio of the rare earth sulfate solution to the mixed precipitant solution is too low or too high, the chloride ion content in the product will increase. Therefore, the preferred flow rate ratio in this invention is within the range of the parameters described above.

[0032] In some embodiments of the present invention, the temperature of the heat preservation reaction is 30-70°C.

[0033] In some embodiments of the present invention, the heat preservation reaction process also includes stirring.

[0034] In some embodiments of the present invention, after the heat preservation reaction is completed, the process further includes dynamic aging, filtration, and washing of the filtered sample.

[0035] This invention controls the RE concentration in the reaction system by controlling factors such as the concentration, relative flow rate, and flow rate of the rare earth sulfate solution and the mixed precipitant solution. 3+ With CO3 2- By using a molar ratio (1:(3-3.6)) and a reaction system pH (5.6-6.2), low-sulfate rare earth carbonates can be obtained, wherein the total rare earth content (REO) is >50wt%, and SO4 content is <50wt%. 2- Content <0.01wt%, low sulfate rare earth carbonate particle size D 50 It is 50-70μm.

[0036] The application further provides a method for reducing the sulfate content in rare earth sulfate, and the low-sulfate rare earth carbonate is prepared by using the method.

[0037] In order to better understand the application, the application is further illustrated below in combination with examples, but the application is not limited to the examples.

[0038] The raw materials and reagents used in the examples can be obtained through the market channel if no special instructions are given.

[0039] Example 1

[0040] 1L of mixed rare earth sulfate solution is taken as the reaction raw material, wherein the rare earth concentration is 42g / L (calculated by REO); 2L of mixed precipitant is configured, and the concentration is 3.8mol / L (the mixed precipitant is prepared by mixing ammonium bicarbonate and ammonia water in a molar ratio of 1:0.8); the above two solutions are added into a reactor in a parallel flow dripping manner to perform a reaction, the volume of the reactor is 5L, the time for controlling the reactor to be full of the solution is 6.25h, the relative flow rate ratio of the rare earth sulfate solution to the mixed precipitant is 1:2.8, deionized water is pre-added into the reactor as a bottom liquid; the reaction temperature is 60℃; and the reaction is continuously stirred. After the feeding is completed, the stirring is continued for 10min, filtration and washing with 0.5L of 90℃ water are performed, and mixed rare earth carbonate solid is obtained, wherein the total rare earth content (REO) is 52wt%, the sulfate content is 98ppm, and the particle size D 50 is 52μm.

[0041] Example 2

[0042] 1L of mixed rare earth sulfate solution is taken as the reaction raw material, wherein the rare earth concentration is 42g / L (calculated by REO); 2L of mixed precipitant is configured, and the concentration is 3.8mol / L (the mixed precipitant is prepared by mixing ammonium bicarbonate and ammonia water in a molar ratio of 1:0.8); the above two solutions are added into a reactor in a parallel flow dripping manner to perform a reaction, the volume of the reactor is 5L, the time for controlling the reactor to be full of the solution is 6.25h, the relative flow rate ratio of the rare earth sulfate solution to the mixed precipitant is 1:2.8, deionized water is pre-added into the reactor as a bottom liquid; the reaction temperature is 60℃; and the reaction is continuously stirred. After the feeding is completed, the stirring is continued for 10min, filtration and washing with 0.5L of 90℃ water are performed, and mixed rare earth carbonate solid is obtained, wherein the total rare earth content (REO) is 52wt%, the sulfate content is 98ppm, and the particle size D 50 is 57μm.

[0043] Example 3

[0044] Take 1L sulfuric acid mixed rare earth solution as the reaction raw material, its rare earth concentration is 1g / L (calculated as REO); configuration mixed precipitator 2L, its concentration is 3.4mol / L (mixed precipitator is prepared by molar ratio = 1:0.6 of ammonium bicarbonate and ammonia water). The above two solutions are added to the reactor in parallel flow dropwise manner to carry out the reaction, the reactor volume is 5L, the time of controlling the reactor to be full of liquid is 6h, the relative flow rate ratio of the rare earth sulfate solution and the mixed precipitator is 1:2.73, deionized water is added in the reactor as the bottom liquid in advance; the reaction temperature is 20℃, and the reaction is continuously stirred. After the feeding is finished, stirring for 10min, filtering, washing with 0.5L 20℃ water to obtain mixed rare earth carbonate solid, wherein the total rare earth content (REO) is 51wt%, the sulfate content is 99ppm, and the particle size D 50 54μm.

[0045] Example 4

[0046] Take 1L sulfuric acid mixed rare earth solution as the reaction raw material, its rare earth concentration is 28g / L (calculated as REO); configuration mixed precipitator 2L, its concentration is 2mol / L (mixed precipitator is prepared by molar ratio = 1:0.4 of ammonium bicarbonate and sodium hydroxide). The above two solutions are added to the reactor in parallel flow dropwise manner to carry out the reaction, the reactor volume is 5L, the time of controlling the reactor to be full of liquid is 4h, the relative flow rate ratio of the rare earth sulfate solution and the mixed precipitator is 1:2.68, deionized water is added in the reactor as the bottom liquid in advance; the reaction temperature is 30℃, and the reaction is continuously stirred. After the feeding is finished, stirring for 10min, filtering, washing with 0.5L 30℃ water to obtain mixed rare earth carbonate solid, wherein the total rare earth content (REO) is 51wt%, the sulfate content is 78ppm, and the particle size D 50 66μm.

[0047] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing low-sulfate rare earth carbonates using a mixed precipitant, characterized in that, After adding rare earth sulfate solution and mixed precipitant solution in a parallel flow manner, the reaction is carried out under heat preservation. HCO3 in the mixed precipitant solution - With OH - The molar ratio is 1:(0.43-1); the concentration of the mixed precipitant solution is 1-4.0 mol / L; The rare earth sulfate solution is a single rare earth sulfate solution or a mixed rare earth sulfate solution; the concentration of the rare earth sulfate solution, calculated as REO, is 1-45 g / L. The flow rate of the mixed precipitant solution is controlled such that the time for the feed liquid to fill the reactor is greater than or equal to 2 hours and less than or equal to 8 hours, and the feed rate is kept uniform; the relative flow rate ratio of the rare earth sulfate solution to the mixed precipitant solution is 1:(2.8-3). Controlling RE in the reaction 3+ With CO3 2- The molar ratio was 1:(3-3.6) and the pH of the reaction system was 5.6-6.2; The temperature of the heat preservation reaction is 30-70℃.

2. The method for preparing low-sulfate rare earth carbonates using a mixed precipitant according to claim 1, characterized in that, The mixed precipitant is two of the following: ammonium bicarbonate, ammonia, sodium bicarbonate, sodium hydroxide, ammonium carbonate, and sodium carbonate, and the mixed precipitant also contains HCO3. - and OH - .

3. The method for preparing low-sulfate rare earth carbonates using a mixed precipitant according to claim 1, characterized in that, The heat preservation reaction process also includes stirring.

4. The method for preparing low-sulfate rare earth carbonates using a mixed precipitant according to claim 1, characterized in that, After the heat preservation reaction is completed, the process also includes dynamic aging, filtration, and washing of the filtered sample.

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