Preparation method of low-chlorine cerous carbonate

Abstract

The invention relates to the technical field of preparation of rare earth compounds, in particular to a preparation method of low-chlorine cerous carbonate. The preparation method comprises the following steps: uniformly mixing a monocarboxyl-containing substance with a cerium chloride solution, adding the mixture and an ammonium bicarbonate solution into a base solution, and reacting to obtain the low-chlorine cerium carbonate. The low-chlorine rare earth carbonate is directly prepared in a high-concentration chlorination system by adopting a simple liquid phase precipitation method; the preparation method is simple in process, stable in product quality, capable of remarkably reducing the use amount of washing water and suitable for industrial production, and is an important method for preparing the high-purity rare earth product precursor.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth compound preparation, in particular to a method for preparing low-chlorine cerium carbonate. Background Art

[0002] With the rapid development of rare earth high-tech applications, people have higher and higher requirements for the quality indicators of rare earth products. For example, when polishing high-precision processes such as chips, the purity requirements of polishing powders are very strict. In recent years, foreign customers have put forward lower requirements for the chloride content in high-purity cerium carbonate or cerium oxide. However, most rare earth extraction and separation currently use hydrochloric acid systems, so the chloride ion content in the product is relatively high.

[0003] CN102978398B discloses a method for significantly reducing the amount of chloride entrainment in the rare earth carbonate crystallization process, the main feature of which is that ultrasound is used to assist in the rare earth carbonate precipitation process, and the corresponding rare earth carbonate with low chloride content is obtained through subsequent aging, crystallization, filtration and washing. This method requires the use of ultrasound assistance and a long aging time, which increases production costs.

[0004] CN105967218B discloses a method for preparing low-chloride cerium carbonate in a hydrochloric acid system, wherein a precipitant is slowly added to a rare earth chloride raw material, and the precipitant addition rate is increased after the crystal is formed intact, and a large amount of pure water is used for multiple stirring and washing, thereby obtaining low-chloride cerium carbonate. In this method, the cerium chloride solution needs to be diluted to 25-40 g / L, and cerium carbonate seeds need to be added, and a large amount of pure water is used for washing, which increases the difficulty of subsequent wastewater treatment and increases production costs.

[0005] CN110372027B discloses a method for preparing low-chloride lutetium oxide, comprising the following steps: mixing lutetium chloride solution with concentrated nitric acid solution to form a stable concentration feed solution, wherein the nitrate concentration in the feed solution is 0.3-2.0 mol / L; then using a co-current precipitation method, mixing bottom water, the feed solution and oxalic acid solution at a temperature of 35-60°C for reaction precipitation, and finally filtering, washing and calcining to obtain low-chloride lutetium oxide. This method uses oxalic acid as a precipitant, which is relatively expensive and toxic, causing environmental pollution; at the same time, the solubility of rare earth oxalate is relatively large, which affects the rare earth yield. Summary of the invention

[0006] In view of this, the present invention provides a method for preparing low-chloride cerium carbonate.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is a method for preparing low-chlorine cerium carbonate, comprising the following steps:

[0009] After the monocarboxyl-containing substance is uniformly mixed with the cerium chloride solution, it is added into the base liquid together with the ammonium bicarbonate solution to react, thereby obtaining the low-chlorine cerium carbonate.

[0010] In some embodiments of the present invention, the monocarboxyl group-containing substance is a monocarboxylic acid and / or a monocarboxylate salt.

[0011] In some embodiments of the present invention, the monocarboxylic acid is acetic acid; and the monocarboxylate salt is an alkali metal acetate or ammonium acetate.

[0012] In some embodiments of the present invention, the amount of the monocarboxyl group-containing substance added is 1% to 10% of the total mass of the rare earth, calculated as REO.

[0013] In some embodiments of the present invention, the concentration of the ammonium bicarbonate solution is 1.0 to 3.3 mol / L.

[0014] In some embodiments of the present invention, Ce in the cerium chloride solution 3+ With the CO3 in the ammonium bicarbonate solution 2- The molar ratio is 1:2.5~3.8.

[0015] In some embodiments of the present invention, the base liquid is water.

[0016] In some embodiments of the present invention, the reaction temperature is 20-80°C.

[0017] The present invention discloses the following technical effects:

[0018] The present invention adopts a simple liquid phase precipitation method to directly prepare low-chlorine carbonate rare earth in a high-concentration, chlorinated system; the preparation method has a simple process, stable product quality, can significantly reduce the amount of washing water, is suitable for industrial production, and is an important method for preparing a high-purity rare earth product precursor.

[0019] The preparation method of the invention can obtain low-chloride cerium carbonate, the chloride content of which is less than 200 ppm. The low-chloride cerium carbonate particles are relatively large and have uniform particle sizes. DETAILED DESCRIPTION

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0025] In the present invention, REO represents a rare earth oxide. Chloride ion may also be referred to as chloride radical.

[0026] The present invention has found that low-chloride cerium carbonate can be prepared by adding a cerium chloride solution containing a monobasic carboxyl substance and an ammonium bicarbonate solution to a base solution for reaction, which is described in detail below.

[0027] The present invention provides a method for preparing low-chlorine cerium carbonate, comprising the following steps:

[0028] After the monocarboxyl-containing substance is uniformly mixed with the cerium chloride solution, it is added into the base liquid together with the ammonium bicarbonate solution to react, thereby obtaining the low-chlorine cerium carbonate.

[0029] In some embodiments of the present invention, the monocarboxyl group-containing substance is a monocarboxylic acid and / or a monocarboxylate salt.

[0030] In some embodiments of the present invention, the monocarboxylic acid is acetic acid; and the monocarboxylate salt is an alkali metal acetate or ammonium acetate.

[0031] In some embodiments of the present invention, the amount of the monocarboxyl-containing substance added is 1% to 10% of the total mass of the rare earth, calculated as REO. It is further preferably 1% to 6%, and more preferably 2% to 5%. During the precipitation process, the surface of the formed cerium carbonate crystals is wrapped by acetic acid molecules and hydrolysis products, which reduces the interfacial energy of the solid-liquid two phases. On the one hand, the supply of solutes at the interface is reduced, the supersaturation S near the phase interface is reduced, and the crystallization rate is reduced, so that chloride ions have sufficient time to escape during the crystallization process, avoiding wrapping and entrainment; on the other hand, the lower interfacial energy reduces the adsorption capacity of chloride ions, and obtains low-chloride cerium carbonate.

[0032] In some embodiments of the present invention, the concentration of the ammonium bicarbonate solution is 1.0 to 3.3 mol / L, preferably 2.5 to 3.0 mol / L.

[0033] In some embodiments of the present invention, Ce in the cerium chloride solution 3+ With the CO3 in the ammonium bicarbonate solution 2- The molar ratio is 1:2.5-3.8. It is preferably 1:2.6-3.4, and more preferably 1:3.0-3.2. A suitable feed ratio helps to improve crystallinity and product purity; at the same time, the feed ratio indirectly reflects the pH value of the precipitation crystallization process. By controlling the pH value of the reaction process, the state of impurity ions in the rare earth feed solution can be changed, so that the impurity ions can be removed in an appropriate form.

[0034] In some embodiments of the present invention, the base liquid is water; specifically, it can be deionized water or pure water.

[0035] In some embodiments of the present invention, the reaction temperature is 20-80° C., more preferably 20-50° C., and more preferably 35-45° C. Any reaction is affected by temperature, which mainly affects the formation and growth of crystals. A suitable temperature ensures a relatively stable supersaturation, thereby affecting the impurity content in the product.

[0036] Controlling the above parameters within the scope of the present invention is beneficial to reducing the crystallization rate and the adsorption of chloride ions by the interface energy during the precipitation process, thereby reducing the chloride content in the cerium carbonate.

[0037] After the reaction is completed, the step of solid-liquid separation is further included, and the solid product is washed with deionized water in an amount of 3 to 6 times the mass of the solid.

[0038] The test method involved in the present invention is:

[0039] Chloride ion content determination: According to the national standard GB / T 12690, the silver nitrate turbidimetry method is used for testing.

[0040] Unless otherwise specified, the raw materials and reagents used in the examples of the present invention can be obtained through commercial sources.

[0041] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] Example 1

[0043] At 45°C, 1.9 g of acetic acid was added to 140 mL of a 280 g / L cerium chloride solution, and then added dropwise to a reactor containing 200 mL of pure water as a base liquid in parallel with 300 mL of a 2.5 mol / L ammonium bicarbonate solution, and mixed for reaction. The reaction end point pH was 6.7 (i.e., the reaction was stopped when the pH of the reaction system was 6.7).

[0044] The precipitated product was vacuum filtered and rinsed with deionized water 6 times the weight of the solid to obtain cerium carbonate with a chloride content of 178 ppm.

[0045] Example 2

[0046] At 45°C, 1.9 g of acetic acid was added to 130 mL of 300 g / L cerium chloride solution, and then added dropwise to a reactor containing 200 mL of pure water as the base liquid in parallel with 300 mL of 2.5 mol / L ammonium bicarbonate solution, and mixed to react. The reaction end point pH was 6.7.

[0047] The precipitated product was vacuum filtered and rinsed with deionized water 6 times the weight of the solid to obtain cerium carbonate with a chloride content of 168 ppm.

[0048] Example 3

[0049] At 25°C, 0.8 g of acetic acid was added to 140 mL of 280 g / L cerium chloride solution, and then added dropwise to a reactor containing 200 mL of pure water as the base liquid in parallel with 300 mL of 2.5 mol / L ammonium bicarbonate solution, and mixed to react. The reaction end point pH was 6.7.

[0050] The precipitated product was vacuum filtered and rinsed with deionized water 6 times the solid mass to obtain cerium carbonate with a chloride content of 153 ppm.

[0051] Example 4

[0052] At 25°C, 0.8 g of acetic acid was added to 130 mL of 300 g / L cerium chloride solution, and then added dropwise to a reactor containing 200 mL of pure water as the base liquid in parallel with 250 mL of 3.0 mol / L ammonium bicarbonate solution, and mixed to react. The reaction end point pH was 6.7.

[0053] The precipitated product was vacuum filtered and rinsed with deionized water 6 times the solid mass to obtain cerium carbonate with a chloride content of 187 ppm.

[0054] Example 5

[0055] At 25°C, 0.8 g of acetic acid was added to 140 mL of 280 g / L cerium chloride solution, and then added dropwise to a reactor containing 200 mL of pure water as the base liquid in parallel with 250 mL of 3.0 mol / L ammonium bicarbonate solution, and mixed to react. The reaction end point pH was 6.7.

[0056] The precipitated product was vacuum filtered and rinsed with deionized water 6 times the weight of the solid to obtain cerium carbonate with a chloride content of 164 ppm.

[0057] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing low-chlorine cerium carbonate, characterized in that: The following steps are involved: After the monocarboxyl-containing substance is uniformly mixed with the cerium chloride solution, it is added into the base liquid together with the ammonium bicarbonate solution to react, thereby obtaining the low-chlorine cerium carbonate.

2. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: The substance containing a monocarboxyl group is a monocarboxylic acid and / or a monocarboxylate salt.

3. The method for preparing low-chlorine cerium carbonate according to claim 2, characterized in that: The monocarboxylic acid is acetic acid; and the monocarboxylate salt is an alkali metal acetate or ammonium acetate.

4. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: Calculated in terms of REO, the added amount of the substance containing a monocarboxyl group is 1% to 10% of the total mass of the rare earth.

5. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: The concentration of the ammonium bicarbonate solution is 1.0-3.3 mol / L.

6. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: The Ce in the cerium chloride solution 3 + With the CO3 in the ammonium bicarbonate solution 2- The molar ratio is 1:2.5~3.

8.

7. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: The base liquid is water.

8. The method for preparing low-chlorine cerium carbonate according to claim 1, characterized in that: The reaction temperature is 20-80°C.