Method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution

Abstract

The invention provides a method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution, and belongs to the technical field of rare earth hydrometallurgy. The method comprises the following steps: adding a low-sulfate rare earth carbonate seed crystal into an ammonium bicarbonate solution to obtain a mixed solution, dropwise adding a low-concentration rare earth sulfate solution into the mixed solution, and reacting to obtain the low-sulfate rare earth carbonate after the reaction endpoint is reached. The low-sulfate rare earth carbonate is synthesized through direct precipitation, the problem that the content of sulfate impurities in the low-concentration rare earth sulfate solution ammonium bicarbonate precipitation method is high is solved, and the problems that in the extraction method transformation process, an organic extraction agent is high in cost, large in loss and the like are solved. The synthesized rare earth carbonate has the advantages of small particles, good dispersity and the like, and the content of SO4 < 2-> in the obtained rare earth carbonate is 1t; and 0.5 wt%.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth hydrometallurgy, and in particular to a method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution. Background Art

[0002] The process of rare earth sulfate solution precipitation-HCl dissolution to convert into rare earth chloride solution or the process of preparing rare earth carbonate from rare earth sulfate solution precipitation will face the problem of high sulfate content in rare earth carbonate, which affects the use of the product. It is necessary to add BaCl2 to remove sulfate process, form a large amount of barium sulfate slag, and cause rare earth loss. Especially for low-concentration rare earth sulfate solution, fine-grained viscous rare earth carbonate will be formed during ammonium bicarbonate precipitation, resulting in insufficient washing and serious entrainment. After washing with a large amount of water, its sulfate content still reaches 2%.

[0003] Patent publication number CN107760867A describes a method for preparing mixed rare earth carbonate using a mixed precipitant in a sulfuric acid system. This method mainly uses a mixed precipitant made of ammonium bicarbonate and ammonia water in proportion to replace the ammonium bicarbonate precipitant, which can effectively increase the concentration of the precipitant, reduce the output of precipitation wastewater, and reduce the subsequent wastewater treatment costs. However, the lowest SO4 2- The content is still greater than 2.42% and has not been effectively reduced.

[0004] The patent with publication number CN109913650A describes a method for converting rare earth sulfate into rare earth chloride, which uses a strong alkaline aqueous solution to partially neutralize one or more organic precipitants selected from p-dodecylphenoxyacetic acid, p-dodecylphenoxypropionic acid and p-dodecylphenoxybutyric acid, and forms a neutralized organic precipitant to precipitate a rare earth sulfate solution to form a complex precipitate, and after eluting with concentrated hydrochloric acid, a rare earth chloride solution with a sodium sulfate mass volume concentration of 0.536g / L is obtained. The essence of this method is to saponify a long molecular chain organic carboxylic acid with sodium hydroxide, and then exchange the organically loaded sodium ions with the rare earth ions, which is consistent with the extraction principle. The problems are that the cost of sodium hydroxide is high, the precipitate is an organic complex, it is difficult to filter the rare earth, the hydrochloric acid backwash forms sodium chloride wastewater, the process is long, and the overall cost is high.

[0005] It can be seen that there has been no sufficient report on the key technical problem of solving the problem of directly precipitating low-concentration rare earth sulfate solution to synthesize low-sulfate rare earth carbonate. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution. The present invention adds the rare earth sulfate solution to the NH4HCO3 solution through reverse precipitation, and the water content of the obtained product is reduced. At the same time, the solution is an alkaline solution, which has a strong effect on SO4 2- The activity of .

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is a method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution. Low-sulfate rare earth carbonate seeds are added to an ammonium bicarbonate solution to obtain a mixed solution, and then the low-concentration rare earth sulfate solution is dripped into the mixed solution to react. After reaching the reaction end point, low-sulfate rare earth carbonate is obtained.

[0009] The second technical solution of the present invention is a method for reducing the sulfate content in sulfated rare earth, and preparing low-sulfate rare earth carbonate using the method for preparing low-sulfate rare earth carbonate using low-concentration rare earth sulfate solution described in the above technical solution.

[0010] According to the sulfate formation mechanism and existence form, the present invention realizes the synthesis of low-sulfate rare earth carbonate by direct precipitation of low-concentration rare earth sulfate solution through the development of a new precipitation method (reverse precipitation is to add rare earth sulfate solution to NH4HCO3) and control technology. The product obtained by the method provided by the present invention has a low water content, which is attributed to the small increase in the particle size and uniform distribution of the product low-sulfate rare earth carbonate. At the same time, the solution is an alkaline solution to SO4 2- Activity has an inhibitory effect.

[0011] The present invention discloses the following technical effects:

[0012] The invention directly precipitates and synthesizes low-sulfate rare earth carbonate, solves the problem of high sulfate impurities in the ammonium bicarbonate precipitation process of low-concentration rare earth sulfate solution, and avoids the problems of high cost and large loss of organic extractants in the process of extraction method transformation.

[0013] The rare earth carbonate synthesized by the present invention has the advantages of small particles and good dispersibility. 2- Content <0.5wt%.

[0014] The invention adopts ammonium bicarbonate as a precipitant to prepare mixed rare earth carbonate, has low raw material cost, low energy consumption at room temperature, simple operation and is easy for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 This is a SEM image of the low-sulfate rare earth carbonate obtained in Example 1 of the present invention.

[0017] Figure 2 The present invention is a process flow chart for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution. DETAILED DESCRIPTION

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0020] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0021] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0022] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0023] The invention provides a method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution. Low-sulfate rare earth carbonate seed crystals are added to an ammonium bicarbonate solution to obtain a mixed solution, and then the low-concentration rare earth sulfate solution is dripped into the mixed solution for reaction. After reaching the reaction end point, the low-sulfate rare earth carbonate is obtained.

[0024] In some embodiments of the present invention, the amount of the low-sulfate rare earth carbonate seed crystals added is 5wt%-20wt% of the theoretical yield of the low-sulfate rare earth carbonate.

[0025] In the present invention, when the amount of low-sulfate rare earth carbonate seeds added is lower than the above parameter range, the product particle size will be small and the sulfate content in the product will increase. When the amount of low-sulfate rare earth carbonate seeds added is higher than the above parameter range, the production efficiency of the reaction container will be wasted.

[0026] In some embodiments of the present invention, the concentration of the ammonium bicarbonate solution is 0.625mol / L-2.5mol / L, preferably 1.25mol / L-2.5mol / L; the amount of the ammonium bicarbonate solution used is: according to the RE in the low concentration rare earth sulfate solution 3+ and CO3 in ammonium bicarbonate solution 2- The molar ratio is 1:3-3.45.

[0027] In the present invention, when the concentration of ammonium bicarbonate is too low, the volume of the supernatant in the obtained reaction solution becomes larger, increasing the amount of wastewater. When the concentration of ammonium bicarbonate is too high, the local reaction is too intense, the content of encapsulated sulfate increases, resulting in an increase in the content of sulfate in the product.

[0028] In the present invention, if the acidity of the feed liquid is high, ammonium bicarbonate needs to neutralize the H in the liquid first. + , the remaining carbonate radicals will react with the rare earth ions. Therefore, the RE in the low concentration rare earth sulfate solution of the present invention 3+ and CO3 in ammonium bicarbonate solution 2- The molar ratio is preferably within the above parameter range so that the feed liquid can react completely.

[0029] In some embodiments of the present invention, the concentration of REO in the low concentration rare earth sulfate solution is 0.2 g / L-10 g / L, preferably 1.5 g / L-2 g / L.

[0030] In the present invention, if the concentration of REO in the low-concentration rare earth sulfate solution is too low, the unit volume production efficiency of the product will decrease and a large amount of waste liquid will be generated. If the concentration of REO in the low-concentration rare earth sulfate solution is too high, the amount of sulfate ions entrained outside the product will increase.

[0031] In some embodiments of the present invention, the dripping rate is:3+ The concentration meter is used and dripped at 0.15-0.8 mol / min.

[0032] In the present invention, if the dripping rate is too fast, it will lead to incomplete reaction, and the crystal particles of the obtained product are small and difficult to filter; if the dripping rate is too slow, the reaction time is too long and the production efficiency is low.

[0033] In some embodiments of the present invention, the reaction temperature is 15-20°C, preferably 15°C.

[0034] In the present invention, if the reaction temperature is too high, the solubility of rare earth sulfate will decrease and crystals will precipitate, while if the temperature is too low, the reaction activity will decrease.

[0035] In some embodiments of the present invention, the reaction process further includes stirring; the stirring speed is 80r / min.

[0036] In some embodiments of the present invention, the pH value at the end point of the reaction is 6.5-7.2.

[0037] In some embodiments of the present invention, after reaching the reaction endpoint, the process further includes sequentially performing the steps of dynamic aging, filtering, and washing.

[0038] In some embodiments of the present invention, the dynamic aging is stirring aging, and the stirring aging time is 5-15 minutes, preferably 10 minutes; the solution used for washing is water; the amount of water used is 1.2-1.5 times the mass of the low-sulfate rare earth carbonate.

[0039] In the low sulfate rare earth carbonate prepared by the method provided by the present invention, SO4 2- Content <0.5wt%, particle size D 50 The nanostructured carbon fiber is 0.5-5um and the REO content is 25-27wt%.

[0040] The present invention also provides a method for reducing the sulfate content in sulfate rare earth, and the method for preparing low-sulfate rare earth carbonate using the low-concentration rare earth sulfate solution described in the above technical solution is used to prepare low-sulfate rare earth carbonate.

[0041] In order to better understand the present invention, the following examples are used to further illustrate the content of the present invention, but the content of the present invention is not limited to the following examples. Figure 1 .

[0042] The raw materials and solvents used in the examples can be obtained through commercial channels.

[0043] Example 1

[0044] Take 1L of lanthanum cerium rare earth sulfate water extract as the reaction raw material, wherein the concentration of REO in the lanthanum cerium rare earth sulfate is 10g / L; prepare 2L of ammonium bicarbonate solution, whose concentration is 2.5mol / L.

[0045] Lanthanum cerium rare earth carbonate (lanthanum cerium rare earth carbonate is used as seed crystal, and the added amount is 15% of the theoretical product mass) is added to the ammonium bicarbonate solution to obtain a mixed solution, and then lanthanum cerium rare earth sulfate water extract is added dropwise to the mixed solution for reaction (with lanthanum cerium rare earth sulfate water extract RE 3+ The concentration meter was used, the dripping rate was 0.8 mol / min), the reaction temperature was 15°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 7.2. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 500 ml of water to obtain the product, lanthanum cerium carbonate with low sulfate radical. The total rare earth content (REO) in the product was 27 wt%, and the sulfate content was 0.48 wt%.

[0046] Depend on Figure 1 It can be seen that the small particles formed under high saturation cannot continue to grow under low saturation conditions, so a large amount of internal and external entrained sulfate will not be caused in the small particle state.

[0047] Example 2

[0048] Take 1L of rare earth sulfate aqueous solution as the reaction raw material (rare earth sulfate aqueous solution is the aqueous solution of mixed rare earth sulfate after concentrate roasting and water washing, containing multiple rare earth elements), wherein the concentration of REO in the rare earth sulfate is 2.5g / L; prepare 2L of ammonium bicarbonate solution, whose concentration is 2mol / L.

[0049] Rare earth carbonate (rare earth carbonate is used as seed crystal, and the amount added is 15% of the theoretical product mass) is added to the ammonium bicarbonate solution to obtain a mixed solution, and then rare earth sulfate water extract is added dropwise to the mixed solution for reaction (the rare earth sulfate water extract has RE 3+ The concentration meter was used, the dripping rate was 0.6 mol / min), the reaction temperature was 15°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 6.8. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 400 ml of water to obtain the product low sulfate rare earth carbonate. The total rare earth content (REO) in the product was 26 wt%, and the sulfate content was 0.26 wt%.

[0050] Example 3

[0051] Take 1L of praseodymium-neodymium rare earth sulfate aqueous solution as the reaction raw material, wherein the concentration of REO in the praseodymium-neodymium rare earth sulfate is 1.5g / L; prepare 2L of ammonium bicarbonate solution, wherein the concentration is 1.25mol / L.

[0052] PrNd carbonate (PrNd carbonate is used as seed crystal, and the amount added is 10% of the theoretical product mass) is added to ammonium bicarbonate solution to obtain a mixed solution, and then PrNd sulfate aqueous solution is added dropwise to the mixed solution for reaction (with PrNd sulfate aqueous solution containing RE 3+ The concentration meter was used, the dripping rate was 0.3 mol / min), the reaction temperature was 20°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 6.7. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 300 ml of water to obtain the product of low sulfate praseodymium neodymium carbonate rare earth. The total rare earth content (REO) in the product was 27wt%, and the sulfate content was 0.24wt%.

[0053] Example 4

[0054] Take 1L of lanthanum cerium rare earth sulfate water extract as the reaction raw material, wherein the concentration of REO in the lanthanum cerium rare earth sulfate is 0.2g / L; prepare 2L of ammonium bicarbonate solution, whose concentration is 0.625mol / L.

[0055] Lanthanum cerium rare earth carbonate (lanthanum cerium rare earth carbonate is used as seed crystal, and the added amount is 5% of the theoretical product mass) is added to the ammonium bicarbonate solution to obtain a mixed solution, and then lanthanum cerium rare earth sulfate water extract is added dropwise to the mixed solution for reaction (with lanthanum cerium rare earth sulfate water extract RE 3+ The concentration meter was used, the dripping rate was 0.3 mol / min), the reaction temperature was 15°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 6.5. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 300 ml of water to obtain the product lanthanum cerium carbonate with low sulfate radical. The total rare earth content (REO) in the product was 27 wt%, and the sulfate content was 0.24 wt%.

[0056] Example 5

[0057] Take 1L of rare earth sulfate aqueous solution as the reaction raw material (rare earth sulfate aqueous solution is the aqueous solution of mixed rare earth sulfate after concentrate roasting and water washing, containing multiple rare earth elements), wherein the concentration of REO in the rare earth sulfate is 10g / L; prepare 2L of ammonium bicarbonate solution, whose concentration is 2.0mol / L.

[0058] Rare earth carbonate (rare earth carbonate is used as seed crystal, and the amount added is 10% of the theoretical product mass) is added to the ammonium bicarbonate solution to obtain a mixed solution, and then rare earth sulfate water extract is added dropwise to the mixed solution for reaction (the rare earth sulfate water extract has a RE content of 10%. 3+The concentration meter was used, the dripping rate was 0.15 mol / min), the reaction temperature was 15°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 7.2. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 700 ml of water to obtain the product low sulfate rare earth carbonate. The total rare earth content (REO) in the product was 26wt%, and the sulfate content was 0.5wt%.

[0059] Comparative Example 1

[0060] Take 1L of lanthanum cerium rare earth sulfate water extract as the reaction raw material, wherein the concentration of REO in the lanthanum cerium rare earth sulfate is 10g / L; prepare 2L of ammonium bicarbonate solution, whose concentration is 2.5mol / L.

[0061] Lanthanum cerium rare earth carbonate (lanthanum cerium rare earth carbonate is used as seed crystal, and the added amount is 15% of the theoretical product mass) is added to the ammonium bicarbonate solution to obtain a mixed solution, and then the mixed solution is added dropwise to the lanthanum cerium rare earth sulfate water extract to react (with the RE in the lanthanum cerium rare earth sulfate water extract) 3+ The concentration meter was used, the dripping rate was 0.8 mol / min), the reaction temperature was 15°C, the stirring speed was 80 r / min, and the pH at the end of the reaction was 7.2. After the feeding was completed, the mixture was stirred for 10 minutes, washed and filtered with 500 ml of water to obtain the product lanthanum cerium carbonate with low sulfate radical. The total rare earth content (REO) in the product was 16 wt%, and the sulfate content was 0.62 wt%.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution, characterized in that: Low-sulfate rare earth carbonate seed crystals are added to an ammonium bicarbonate solution to obtain a mixed solution, and then a low-concentration rare earth sulfate solution is dripped into the mixed solution for reaction, and after reaching the reaction end point, low-sulfate rare earth carbonate is obtained.

2. The method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution according to claim 1, characterized in that: The amount of the low sulfate rare earth carbonate seed crystals added is 5wt%-20wt% of the theoretical yield of the low sulfate rare earth carbonate.

3. The method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution according to claim 1, characterized in that: The concentration of the ammonium bicarbonate solution is 0.625 mol / L-2.5 mol / L; the amount of the ammonium bicarbonate solution used is: according to the RE content in the low concentration rare earth sulfate solution 3+ and CO3 in ammonium bicarbonate solution 2- The molar ratio is 1:3-3.

45.

4. The method for preparing low-sulfate rare earth carbonate from a low-concentration rare earth sulfate solution according to claim 1, characterized in that: The concentration of REO in the low-concentration rare earth sulfate solution is 0.2 g / L-10 g / L.

5. The method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution according to claim 1, characterized in that: The dripping rate is: 3+ The concentration meter is used and dripped at 0.15-0.8 mol / min.

6. The method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution according to claim 1, characterized in that: The reaction temperature is 15-20°C.

7. The method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution according to claim 1, characterized in that: The pH value at the end point of the reaction is 6.5-7.

2.

8. The method for preparing low-sulfate rare earth carbonate from low-concentration rare earth sulfate solution according to claim 1, characterized in that: After reaching the reaction endpoint, the method further includes the steps of dynamic aging, filtering and washing.

9. A method for reducing the sulfate content in sulfate rare earth, characterized in that: The method according to any one of claims 1 to 8 is used to prepare low-sulfate rare earth carbonate.

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