Method for recovering and preparing cerium fluoride from bastnaesite

Abstract

The invention belongs to the field of rare earth metallurgy, and discloses a method for recovering and preparing cerium fluoride from bastnaesite, which comprises the following steps: grinding the bastnaesite by a Raymond mill to obtain ground mineral powder; oxidizing and roasting the ground ore powder to obtain oxidized and roasted ore; water is added into the oxidized roasted ore for size mixing, first-time acid dissolution is carried out under the low-acid condition, and first-time acid leaching liquid and first-time acid leaching residues are obtained through filtering; dilute acid is added into the first-time acid leaching residues for size mixing, second-time acid dissolution is carried out under the low-temperature and high-acid condition, and second-time acid leaching liquid and second-time acid leaching residues are obtained through filtering; and adding alkali into the second acid leaching solution to adjust the acidity, controlling the deposition condition to deposit cerium fluoride, and filtering and washing to obtain cerium fluoride. According to the method, the cerium fluoride product with the purity being 99% or above can be recycled and prepared, and comprehensive recycling of rare earth and fluorine resources in bastnaesite is achieved.

Description

Technical Field

[0001] The invention belongs to the field of rare earth metallurgy and relates to a method for recovering and preparing cerium fluoride from bastnaesite. Background Art

[0002] Bastnaesite, the primary mineral used in rare earth smelting and separation, supplies over 90% of the world's light rare earth resources. Depending on the beneficiation process, it can be divided into bastnaesite gravity separation and flotation concentrate. Both concentrates generally utilize an oxidative roasting-hydrochloric acid leaching and decomposition process. This process first roasts the bastnaesite concentrate at 500-600°C to produce a smelted ore. The smelted ore undergoes hydrochloric acid dissolution, alkaline conversion, and hydrochloric acid leaching to produce a cerium-low, lanthanum-rich rare earth feed and a cerium-rich slag. This smelt can leach over 95% of the high-value praseodymium and neodymium elements. However, approximately 80% of the cerium remains in the cerium-rich slag, and approximately 80% of the fluorine enters the wastewater during the alkaline conversion process, posing environmental risks and resulting in a significant waste of cerium and fluorine resources.

[0003] CN109266838A provides a method for treating bastnaesite and mixed ores containing bastnaesite. The method comprises roasting the bastnaesite to obtain a roasted product, leaching the roasted product with hydrochloric acid to obtain a leached product, performing solid-liquid separation on the leached product to obtain a leachate and a leached residue, performing selective precipitation on the leachate to obtain a precipitate product, and performing solid-liquid separation on the precipitate product to obtain a cerium fluoride precipitate and a cerium-low rare earth chloride solution. The reaction temperature of the selective precipitation treatment is higher than that of the hydrochloric acid leaching. The technical solution of this invention is to decompose the bastnaesite by full leaching with hydrochloric acid, followed by selective precipitation of the acid leachate, and to recover a high-purity cerium fluoride product. However, in order to suppress the reduction of tetravalent cerium during the hydrochloric acid dissolution process, this technical solution requires the addition of additional compounds containing sulfate or nitrate as auxiliary agents. Furthermore, during the selective deposition process of the acid leaching solution, reducing substances are also required to control the zeta potential of the leaching solution to below 1.6V in order to obtain a high-purity cerium fluoride product. The addition of these substances not only introduces new non-rare earth impurities into the acid leaching solution after deposition, but also increases the cost of auxiliary materials and the operational requirements for the recovery and preparation of cerium fluoride. Furthermore, the acid leaching solution deposition process requires the control of a relatively high deposition temperature, which results in higher energy consumption costs and further compresses the profit margins of the recovery process. Summary of the Invention

[0004] The purpose of the present invention is to develop a method for recovering and preparing cerium fluoride from bastnaesite that is easier to operate and has lower costs. While decomposing the bastnaesite to dissolve rare earths, the fluorine and cerium resources in the bastnaesite are recovered, thereby realizing the comprehensive utilization of the bastnaesite resources.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: A method for recovering and preparing cerium fluoride from bastnaesite comprises the following steps: (1) The fluorocarbon cerium ore is ground by Raymond mill to obtain ground ore powder; (2) Oxidative roasting of ground ore powder to obtain oxidized roasted ore; (3) Add water to the oxidized roasted ore to prepare the slurry, carry out the first acid dissolution under low acid conditions, and filter to obtain the first acid leaching liquid and the first acid leaching residue; (4) Add dilute acid to the first acid leaching residue to make a slurry, perform a second acid dissolution under low temperature and high acid conditions, and filter to obtain the second acid leaching liquid and the second acid leaching residue; (5) After the acidity of the second acid leaching solution is adjusted by adding alkali, the deposition conditions are controlled to deposit cerium fluoride, and cerium fluoride can be obtained after filtering and washing.

[0006] Preferably, the particle size of the ground mineral powder after Raymond milling is 13-125 μm, preferably 44-74 μm.

[0007] Preferably, the ground ore powder is roasted in normal air with oxygen, the roasting temperature is 480-600°C, preferably 500-550°C, the roasting time is 1-4h, preferably 2-3h, and the proportion of tetravalent cerium in the total cerium in the rare earth distribution after roasting is 90%-100%, preferably 94-98%.

[0008] Preferably, in step (3), water is added to the oxidized roasted ore and / or the washing water in step (5) is added to adjust the slurry, and the slurry solid-liquid ratio is 1:1-1:5, preferably 1:1-1:3.

[0009] Preferably, in step (3), after the oxidized roasted ore is slurried, the first acid dissolution is carried out under low-acid conditions, and the acid used is hydrochloric acid, the hydrochloric acid concentration is 0.5-2 mol / L, preferably 1-1.5 mol / L, the amount of hydrochloric acid added is 2.0-3.5 times the molar amount of trivalent rare earth contained in the oxidized roasted ore, preferably 2.8-3.2 times, the acid dissolution temperature is 20-40°C, preferably 25-30°C, and the acid addition speed is controlled to maintain the feed liquid temperature during acid addition. After the acid addition is completed, stirring is continued for 0.5-3h, preferably 1-1.5h.

[0010] Preferably, the first acid leaching residue is slurried with dilute acid, the dilute acid is hydrochloric acid, the concentration is 0.3-1.0 mol / L, preferably 0.5-0.7 mol / L, and the slurry liquid-to-solid ratio is 1:1-3, preferably 1:1.5-2; after slurrying, a second acid dissolution is carried out under low temperature and high acid conditions, the temperature is 0-15°C, preferably 5-10°C, the acid used is hydrochloric acid, the hydrochloric acid concentration is 4-8 mol / L, preferably 5-6 mol / L, the amount of hydrochloric acid added is 4.0-5.0 times the total rare earth amount of the added ore sample minus the amount of hydrochloric acid added in the first acid dissolution and the amount of hydrochloric acid added when the first acid leaching residue is slurried, preferably 4.3-4.8 times, the acid addition speed is controlled to maintain the feed liquid temperature during acid addition, and stirring is continued for 5-30 min, preferably 10-15 min after the acid addition is completed.

[0011] Preferably, the acidity of the second acid leaching solution is adjusted by adding alkali, which is one of sodium hydroxide, ammonia water, and cerium carbonate. The acidity is adjusted to 0.1-0.5 mol / L, preferably 0.25-0.35 mol / L. The deposition conditions are controlled as follows: the deposition temperature is 15-35° C., preferably 20-25° C., and the deposition time is 5-30 min, preferably 10-15 min.

[0012] Preferably, after deposition, the cerium fluoride is filtered, and the pore size of the filtering equipment is 0.1-0.5 μm, preferably 0.2-0.3 μm. After filtration, the cerium fluoride is washed by acid washing and water washing, and the washing liquid-to-solid ratio is 3:1-10:1, preferably 4-6:1. The acid washing is 0.1-0.5 mol / L hydrochloric acid, preferably 0.3-0.4 mol / L, and the washing method is agitation washing, and the number of washing times is 1. The number of water washing times is 1-4 times, preferably 2-3 times, and the washing method is agitation washing or rinsing.

[0013] The technical solution of the present invention is aimed at the comprehensive recovery of cerium fluoride resources in fluorocarbon cerium ore, and a more easily controlled and lower-cost recovery and preparation process has been developed. Under relatively mild deposition conditions, a cerium fluoride product with a purity of more than 99% can be prepared. In the first acid leaching process, a low-cerium lanthanum-rich rare earth solution mainly containing lanthanum, praseodymium, and neodymium is leached with low acid. The first acid leaching residue suppresses the reduction of tetravalent cerium at low temperature to dissolve fluorine and cerium to obtain a second acid leaching solution with high fluorine and high cerium. The acidity of the second acid leaching solution is adjusted by adding alkali to avoid the redissolution of the deposited cerium fluoride. The deposited cerium fluoride is first stirred and washed with acid to remove the rare earth hydroxides precipitated by hydrolysis during the acid adjustment process. Since most of the non-cerium rare earths have been dissolved in the first acid leaching process, the second acid leaching solution is mainly composed of cerium and fluorine. Therefore, the influence of non-cerium rare earth and fluorine deposition on the purity of the cerium fluoride product can be reduced during the deposition process. In addition to the acids and bases commonly used in extraction and separation production, the entire method does not require the addition of exogenous additives, which can avoid the impact on the smelting and separation of the rare earth liquid after deposition. At the same time, the deposition process does not require the control of Zeta potential, the operation is simpler, and the deposition conditions are milder, which is a significant improvement over existing technologies.

[0014] The beneficial effects and implementation methods of the present invention are as follows: (1) No additives are required during the hydrochloric acid leaching process: the reduction of tetravalent cerium is suppressed by low-temperature leaching; (2) The deposition conditions are reduced from over 80°C to 15-35°C, resulting in lower energy consumption: the problem of cerium fluoride redissolution that may occur during the deposition process is solved by adjusting the acidity of the acid leaching solution by alkali, so there is no need to adjust the solubility product in the cerium fluoride redeposition solution by higher temperature; (3) There is no need to control the Zeta potential during the deposition process, and the purity of cerium fluoride is higher: most of the lanthanum, praseodymium, and neodymium elements are leached out through the first acid leaching, so that the rare earth distribution in the second acid leaching solution is mainly cerium, avoiding the influence of the combination of non-cerium rare earths and fluorine on the purity of cerium fluoride during the deposition process. At the same time, the acidity of the acid leaching solution is adjusted by alkali to avoid the redissolution of cerium fluoride after deposition. Therefore, there is no need to control the Zeta potential for selective deposition to obtain a purity of cerium fluoride of more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0016] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0017] A method for recovering and preparing cerium fluoride from bastnaesite comprises the following steps: (1) The fluorocarbon cerium ore is ground by Raymond mill to obtain ground ore powder; (2) Oxidative roasting of ground ore powder to obtain oxidized roasted ore; (3) Add water to the oxidized roasted ore to prepare the slurry, carry out the first acid dissolution under low acid conditions, and filter to obtain the first acid leaching liquid and the first acid leaching residue; (4) Add dilute acid to the first acid leaching residue to make a slurry, perform a second acid dissolution under low temperature and high acid conditions, and filter to obtain the second acid leaching liquid and the second acid leaching residue; (5) After the acidity of the second acid leaching solution is adjusted by adding alkali, the deposition conditions are controlled to deposit cerium fluoride, and cerium fluoride can be obtained after filtering and washing.

[0018] The following is a detailed description of the method for recovering and preparing cerium fluoride from bastnaesite provided by the present invention in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0019] Example 1: The analysis results of the fluorocarbon cerium ore gravity separation concentrate provided by a rare earth mine in Sichuan are shown in Tables 1 and 2.

[0020] Table 1 Main components of bastnaesite gravity concentrate (%) Table 2 Rare earth distribution of bastnaesite gravity concentrate (%) The fluorocarbon cerium ore gravity concentrate was ground and passed through a 200-mesh sieve (74 μm). 100 g of the sieved ore was roasted in an air atmosphere at 500 ° C for 2 h. The obtained oxidized roasted ore was slurried with water at a solid-liquid ratio of 1:1. Under the reaction temperature of 25 ° C, 636 ml of 1 mol / L hydrochloric acid solution was added at 3.0 times the molar amount of trivalent rare earth in the ore using a peristaltic pump for the first acid dissolution. After the acid addition was completed, stirring was continued for 1 h and then filtered to obtain the first acid leaching solution and the first acid leaching residue. The first acid leaching residue was slurried with 0.5 mol / L dilute hydrochloric acid at a solid-liquid ratio of 1:1. 284 ml of 4 mol / L hydrochloric acid was added at 10 ° C. (4.5 times the total rare earth molar amount minus the amount of hydrochloric acid added in the first acid dissolution and the amount of hydrochloric acid added when the first acid leaching residue was slurried) was acid dissolved for the second time. After the acid addition was completed, stirring was continued for 5 minutes and then filtered to obtain the second acid leaching solution and the second acid leaching residue. Ammonia water was immediately added to the second acid leaching solution to adjust the acidity to 0.28 mol / L. After sedimentation at 25°C for 10 minutes, it was filtered using a 0.1um filter paper. The obtained filter residue was first washed once with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:10, and then rinsed twice with water at a solid-liquid ratio of 1:10. After filtration and drying, 17.5 g of cerium fluoride product was obtained. The analysis results are shown in Table 3.

[0021] Table 3 Analysis results of cerium fluoride Example 2: The above-mentioned fluorocarbon cerium ore gravity separation concentrate is still used, and the ore powder is ground and passed through a 200-mesh sieve (74μm). After screening, 100g of the ore powder is taken and roasted in an air atmosphere at 500°C for 2h. The obtained oxidized roasted ore powder is slurried with water at a solid-liquid ratio of 1:1. Under the reaction temperature of 20°C, 297ml of 2mol / L hydrochloric acid solution is added at 2.8 times the molar amount of trivalent rare earth in the ore powder using a peristaltic pump for the first acid dissolution. After the acid addition is completed, stirring is continued for 1h and then filtered to obtain the first acid leaching liquid and the first acid leaching residue. The first acid leaching residue is slurried with 0.6mol / L dilute hydrochloric acid at a solid-liquid ratio of 1:1, and 190ml of 6mol / L hydrochloric acid is added at 5°C. l (4.3 times the total rare earth molar amount minus the amount of hydrochloric acid added in the first acid dissolution and the amount of hydrochloric acid added when the first acid leaching residue was slurried) for the second acid dissolution. After the acid addition was completed, stirring was continued for 15 minutes and then filtered to obtain the second acid leaching solution and the second acid leaching residue. Ammonia water was immediately added to the second acid leaching solution to adjust the acidity to 0.18 mol / L. After sedimentation at 15°C for 30 minutes, it was filtered with 0.25um filter paper. The obtained filter residue was first washed once with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:10, and then rinsed twice with water at a solid-liquid ratio of 1:10. After filtration and drying, 16.3 g of cerium fluoride product was obtained. The analysis results are shown in Table 4.

[0022] Table 4 Analysis results of cerium fluoride Comparative Example 1: The above-mentioned fluorocarbon cerium ore gravity separation concentrate was still used, and the ore powder was ground and passed through a 200-mesh sieve (74 μm). After screening, 100 g of the ore powder was taken and roasted in an air atmosphere at 500 ° C for 2 h. The obtained oxidative roasted ore powder was slurried with water at a solid-liquid ratio of 1:1. Under the reaction temperature of 20 ° C, a peristaltic pump was used to add 876 ml of 2 mol / L hydrochloric acid solution at 4.3 times the total rare earth molar amount in the ore powder for the first acid dissolution. After the acid addition was completed, stirring was continued for 1 h and then filtered to obtain an acid leaching solution. Ammonia water was immediately added to the acid leaching solution to adjust the acidity to 0.18 mol / L. After sedimentation at 15 ° C for 30 min, it was filtered with 0.25 μm filter paper. The obtained filter residue was first washed with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:10, and then rinsed twice with water at a solid-liquid ratio of 1:10. After filtration and drying, only 1.2 g of cerium fluoride product was obtained. The analysis results are shown in Table 5.

[0023] Table 5 Analysis results of cerium fluoride Compared with Example 2, the amount of cerium fluoride deposited from the acid leaching solution in Comparative Example 1 is less and the purity is poor. The reaction temperature of 20° C. is close to the deposition condition of cerium fluoride. Most of the cerium fluoride is deposited in the acid leaching residue during the acid leaching process.

[0024] Comparative Example 2: The above-mentioned fluorocarbon cerium ore gravity separation concentrate was still used, and the ore powder was ground and passed through a 200-mesh sieve (74 μm). After screening, 100 g of the ore powder was taken and roasted in an air atmosphere at 500 ° C for 2 h. The obtained oxidative roasted ore powder was slurried with water at a solid-liquid ratio of 1:1, and then 292 ml of 6 mol / L hydrochloric acid (4.3 times the total rare earth molar amount) was added at 5 ° C for acid dissolution. After the acid addition was completed, stirring was continued for 15 minutes and then filtered to obtain an acid leaching solution and acid leaching residue. Ammonia water was immediately added to the leaching solution to adjust the acidity to 0.18 mol / L. After sedimentation at 15 ° C for 30 minutes, it was filtered with 0.25 μm filter paper. The obtained filter residue was first washed once with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:10, and then rinsed twice with water at a solid-liquid ratio of 1:10. After filtration and drying, 16.6 g of cerium fluoride product was obtained. The analysis results are shown in Table 6.

[0025] Table 6 Analysis results of cerium fluoride The acid leaching solution deposited in Comparative Example 2, obtained under low-temperature acid leaching conditions, had a quality similar to that of the cerium fluoride obtained in Example 2, but its purity was lower. Although low-temperature acid leaching suppressed cerium fluoride deposition during the acid leaching process and improved cerium fluoride recovery, the purity of the deposited cerium fluoride was compromised due to the lack of separation of non-cerium rare earth elements.

[0026] Comparative Example 3 The above-mentioned fluorocarbon cerium ore gravity separation concentrate is still used, and the ore powder is ground and passed through a 200-mesh sieve (74μm). After screening, 100g of the ore powder is taken and roasted in an air atmosphere at 500℃ for 2h. The obtained oxidized roasted ore powder is slurried with water at a solid-liquid ratio of 1:1. Under the reaction temperature of 20℃, 297ml of 2mol / L hydrochloric acid solution is added at 2.8 times the molar amount of trivalent rare earth in the ore powder using a peristaltic pump for the first acid dissolution. After the acid addition is completed, stirring is continued for 1h and then filtered to obtain the first acid leaching solution and the first acid leaching residue. The first acid leaching residue is slurried with 0.6mol / L dilute hydrochloric acid at a solid-liquid ratio of 1:1 and stirred at 5℃. 190 ml of 6 mol / L hydrochloric acid (4.3 times the total rare earth molar amount) was added for the second acid dissolution. After the acid addition was completed, stirring was continued for 15 minutes and then filtered to obtain the second acid leaching solution and the second acid leaching residue. Ammonia water was immediately added to the second acid leaching solution to adjust the acidity to 0.18 mol / L. After sedimentation at 85°C for 30 minutes, it was filtered using a 0.25 μm filter paper. The obtained filter residue was first washed once with 0.5 mol / L hydrochloric acid at a solid-liquid ratio of 1:10, and then rinsed twice with water at a solid-liquid ratio of 1:10. After filtration and drying, 17.1 g of cerium fluoride product was obtained. The analysis results are shown in Table 7.

[0027] Table 7 Analysis results of cerium fluoride The quality and purity of cerium fluoride obtained in Comparative Example 3 are similar to those in Example 2. This indicates that the temperature conditions set in Example 2 can already meet the deposition requirements. Although higher temperature deposition conditions have little effect on the deposition of cerium fluoride, they increase energy consumption costs.

Claims

1. A method for recovering and preparing cerium fluoride from bastnaesite, characterized in that: The following steps are involved: (1) The fluorocarbon cerium ore is ground by Raymond mill to obtain ground ore powder; (2) Oxidative roasting of ground ore powder to obtain oxidized roasted ore; (3) Adding water to the oxidized roasted ore to prepare a slurry, performing the first acid dissolution under low acid conditions, filtering to obtain the first acid leaching solution and the first acid leaching residue, wherein the acid used is hydrochloric acid, the concentration of hydrochloric acid is 0.5-2 mol / L, the amount of hydrochloric acid added is 2.0-3.5 times the molar amount of trivalent rare earth contained in the oxidized roasted ore, and the acid dissolution temperature is 20-40°C; (4) Add dilute acid to the first acid leaching residue to make a slurry, carry out a second acid dissolution under low temperature and high acid conditions, filter to obtain the second acid leaching solution and the second acid leaching residue, wherein the low temperature and high acid conditions are to add hydrochloric acid with a concentration of 4-8 mol / L, and the amount of hydrochloric acid added is 4.0-5.0 times the total amount of rare earth in the added ore sample minus the amount of hydrochloric acid added in the first acid dissolution and the amount of hydrochloric acid added when making a slurry for the first acid leaching residue, and the acid dissolution temperature is 0-15°C; (5) After the acidity of the second acid leaching solution is adjusted by adding alkali, the deposition conditions are controlled to deposit cerium fluoride, and cerium fluoride can be obtained after filtering and washing. The acidity is adjusted to 0.1-0.5 mol / L and the deposition temperature is 15-35°C.

2. The method according to claim 1, characterized in that The bastnaesite includes one or both of gravity concentrate and flotation concentrate obtained in a beneficiation process.

3. The method according to claim 1, characterized in that The particle size of the ground mineral powder after Raymond mill is 13-125μm.

4. The method according to claim 1, wherein The ground ore powder is roasted in an aerobic manner under a normal air atmosphere at a temperature of 480°C-600°C and a time of 1-4 hours. After roasting, the proportion of tetravalent cerium in the total cerium in the rare earth distribution is 90%-100%.

5. The method according to claim 1, wherein In step (3), water is added to the oxidized roasted ore and / or the washing water in step (5) to prepare the slurry, and the solid-liquid ratio of the slurry is 1:1-1:

5.

6. The method according to claim 1, characterized in that In step (3), the acid addition rate is controlled to maintain the temperature of the feed solution, and stirring is continued for 0.5-3 hours after the acid addition is completed.

7. The method according to claim 1, characterized in that The dilute acid used for the first acid leaching residue slurrying is hydrochloric acid with a concentration of 0.3-1.0 mol / L and a slurrying liquid-to-solid ratio of 1:1-3.

8. The method according to claim 1, characterized in that In step (4), the acid addition rate is controlled during the second acid dissolution to maintain the temperature of the liquid, and stirring is continued for 5-30 minutes after the acid addition is completed.

9. The method according to claim 1, characterized in that In step (5), the base is one of sodium hydroxide, ammonia water, and cerium carbonate; and the deposition time is 5-30 min.

10. The method according to claim 1, characterized in that In step (5), the pore size of the filtering equipment is 0.1-0.5 μm, and the washing of cerium fluoride after filtration includes acid washing and water washing, the washing liquid-solid ratio is 3:1-10:1, the acid washing is 0.1-0.5 mol / L hydrochloric acid, the washing number is 1, and the water washing number is 1-4 times.

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