Method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching

Abstract

The present invention provides a method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt to assist sulfuric acid and hydrochloric acid mixed enhanced leaching, comprising the following steps: using a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate to leach the rare earth ores, filtering, and obtaining a first filtrate; adding calcium sulfate crystal seeds to the first filtrate, filtering, obtaining calcium sulfate crystals and a second filtrate; adding sodium sulfate to the second filtrate, filtering, obtaining a third filtrate and rare earth sulfate double salt; adding sodium fluoride to the third filtrate, and adding a pH regulator to adjust the pH to 3-5, filtering, and obtaining cryolite. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt to assist sulfuric acid and hydrochloric acid mixed enhanced leaching of rare earth ores of the present invention has a higher rare earth leaching rate, lower cost and a greener environmental protection effect.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth hydrometallurgy, and in particular to a method for recovering rare earth and fluorine-aluminum by mixed enhanced leaching of rare earth ores with sulfuric acid and hydrochloric acid assisted by aluminum salt. Background Art

[0002] Baotou rare earth concentrate is a mixed rare earth ore formed by bastnaesite and monazite in different proportions. The chemical properties of bastnaesite and monazite are different, and the difficulty of decomposition is different, which makes the decomposition and separation technology of Baotou rare earth ore difficult. At present, the industry mainly uses acid and alkali methods to decompose Baotou rare earth concentrate, and the most representative ones are high-temperature concentrated sulfuric acid roasting method and sodium hydroxide decomposition method. More than 90% of Baotou rare earth concentrate is decomposed by high-temperature concentrated sulfuric acid roasting method. This is because the high-temperature concentrated sulfuric acid roasting method is simple to operate, has low requirements for rare earth grade, can be continuously produced, and has a high rare earth recovery rate. The disadvantages of the high-temperature concentrated sulfuric acid roasting method are high roasting temperature, large amount of radioactive waste residue, and a large amount of hydrogen fluoride and sulfur oxide mixed gas. A large amount of water is required to cool down and absorb waste gas, which is not conducive to environmental protection. The sodium hydroxide decomposition method does not produce harmful acidic gases and ammonia nitrogen wastewater. NaF and Na3PO4 in the wastewater can be recycled by causticization, which can reduce the pollution of fluorine to the environment. However, the sodium hydroxide decomposition method has high requirements for the grade of rare earth concentrate, generally above 55%, is not easy to operate continuously, consumes too high alkali concentration, takes a long time to decompose the minerals, and the rare earths, Th, F, etc. are relatively dispersed, the rare earth recovery rate is low, and the cost is high, thus limiting the large-scale application of the sodium hydroxide decomposition method.

[0003] With the development and progress of society, the country's requirements for environmental protection in industrial production processes are becoming more and more stringent. Resource waste and environmental pollution have become bottlenecks restricting the healthy and sustainable development of the rare earth industry. Therefore, it is necessary to develop new rare earth separation and recovery processes to achieve lower cost and greener environmental protection in the recovery of rare earth and associated resources in rare earth concentrates.

[0004] Application Contents

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a method for recovering rare earth and fluorine-aluminum from rare earth ores by mixed enhanced leaching of rare earth ores with sulfuric acid and hydrochloric acid assisted by aluminum salt, aiming to recover rare earth and aluminum-fluoride from rare earth ores at a lower cost and in a greener and more environmentally friendly manner while ensuring the rare earth leaching rate.

[0006] The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching provided by the present invention comprises the following steps:

[0007] The rare earth ore is leached with a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate, and filtered to obtain a first filtrate;

[0008] Add calcium sulfate seed crystals to the first filtrate, filter, and obtain calcium sulfate crystals and a second filtrate;

[0009] adding sodium sulfate to the second filtrate, filtering, and obtaining a third filtrate and rare earth sulfate double salt; and

[0010] Sodium fluoride is added to the third filtrate, and a pH regulator is added to adjust the pH to 3-5, and the mixture is filtered to obtain cryolite.

[0011] Furthermore, in the mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate, the concentration range of the sulfuric acid is 2-3.5 mol / L, the concentration range of the hydrochloric acid is 0.3-2 mol / L, and the concentration range of the aluminum sulfate is 0.15-0.3 mol / L.

[0012] Furthermore, in the leaching process, the leaching temperature is 120-140°C, the leaching time is 2-3h, the stirring speed is 100-300r / min, and the liquid-solid ratio is 20-44:1.

[0013] Furthermore, the calcium sulfate seed crystals are calcium sulfate dihydrate and / or calcium sulfate, and the added amount of the calcium sulfate seed crystals is 0.05%-0.5% of the mass of the first filtrate.

[0014] Furthermore, the step of "adding sodium sulfate to the second filtrate" includes: adding sodium sulfate to the second filtrate at a temperature of 20-100°C, stirring for 20-50 minutes, and the mass ratio of the sodium sulfate to the rare earth oxide in the second filtrate is 2-3:1.

[0015] Furthermore, the amount of sodium fluoride added is 5-7 times the aluminum ion concentration in the third filtrate.

[0016] Furthermore, the pH adjuster is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0017] Furthermore, in the step of “adding sodium fluoride to the third filtrate, filtering, and obtaining cryolite”, the heating reaction is stirring at a temperature of 20-100° C. for 50-70 minutes.

[0018] In the technical solution of the present invention, a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate is used to leach the rare earth ore, and the mixture is filtered to obtain a first filtrate. The aluminum ions in the aluminum sulfate can not only promote the separation of fluorocarbon cerium ore and monazite, but also fully complex with the fluorine ions in the leaching solution to form a soluble complex, stabilize the fluorine in the filtrate, and avoid the fluorine ions from escaping to form hydrogen fluoride and polluting the environment. With the assistance of aluminum sulfate, the hydrogen ions provided by sulfuric acid and hydrochloric acid can separate all or almost all of the fluorocarbon cerium ore from monazite in the rare earth ore to obtain a first filtrate and a monazite filter residue. First, monazite is separated from fluorocarbon cerium ore to avoid fluorocarbon cerium ore affecting the post-treatment of monazite, which is conducive to obtaining high-purity trisodium phosphate by alkaline decomposition. The cooperation of sulfuric acid, hydrochloric acid and aluminum sulfate can not only achieve a higher rare earth leaching rate (the leaching rate of fluorocarbon cerium ore is not less than 97%), but also stabilize the fluorine ions in the filtrate to prevent the fluorine ions from escaping and polluting the environment, and can also save the step of recovering rare earths by extraction due to excessive addition of hydrochloric acid. Calcium sulfate seeds are added to the first filtrate to generate calcium sulfate crystal precipitation to recover calcium, so as to remove most of the calcium ions in the first filtrate and obtain the second filtrate. Sodium sulfate is added to the second filtrate, and the reaction is heated and filtered to obtain the third filtrate and rare earth sulfate complex salt (chemical formula is NaRE (SO4) 2), and the rare earth is recovered in the form of complex salt. Sodium fluoride is added to the third filtrate, the pH is adjusted to 3-5, and the reaction is heated and filtered to obtain cryolite (chemical formula is Na3AlF6) to recover aluminum fluoride, which can prevent the generation of fluorine waste gas. The method of the present invention for recovering rare earth and fluorine-aluminum by aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching of rare earth ores does not require high-temperature treatment, is simple to operate, can be produced continuously, has a high rare earth recovery rate, and does not generate pollutants such as radioactive waste residues, hydrogen fluoride or nitrogen wastewater. Under the premise of ensuring the rare earth leaching rate, the rare earth and aluminum-fluoride in the rare earth ores are recovered at a lower cost and in a greener and more environmentally friendly manner (nearly zero emission). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The present invention is a process flow chart of a method for recovering rare earth and fluorine-aluminum by using aluminum salt to assist sulfuric acid and hydrochloric acid mixed enhanced leaching of rare earth ores.

[0021] Figure 2 The present invention is a process flow chart of a method for recovering rare earth and fluorine-aluminum by using aluminum salt to assist sulfuric acid and hydrochloric acid mixed enhanced leaching of rare earth ores in accordance with a specific embodiment of the present invention.

[0022] Figure 3 It is a comparison curve chart of the overflow of fluoride ions over time in Comparative Examples 1 to 2 and Example 2.

[0023] Figure 4 This is a graph showing the effect of the ratio of the sulfate acid equivalent concentration in Comparative Example 3 and Example 3 on the rare earth leaching rate.

[0024] Figure 5 H in Example 4 + Effect of concentration on rare earth leaching rate.

[0025] Figure 6 Graph showing the effect of aluminum sulfate concentration on rare earth leaching rate in Example 5.

[0026] Figure 7 This is a graph showing the effect of the leaching reaction temperature on the rare earth leaching rate in Example 6.

[0027] Figure 8 This is a graph showing the effect of the liquid-to-solid ratio on the rare earth leaching rate in Example 7.

[0028] Fig. 9 This is a graph showing the effect of reaction time on rare earth leaching rate in Example 8.

[0029] Fig.10 This is a graph showing the effect of the mass ratio of Na2SO4 to RE2O3 on the rare earth recovery rate in Example 9.

[0030] Fig.11 This is a graph showing the effect of the reaction time of rare earth sulfate double salt precipitation on the rare earth recovery rate in Example 10.

[0031] Fig.12 This is a graph showing the effect of the reaction temperature of rare earth sulfate double salt precipitation on the rare earth recovery rate in Example 11.

[0032] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the present invention, the descriptions involving "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] Ginseng Figure 1-2 An embodiment of the present invention provides a method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching, comprising the following steps:

[0036] Step S1: In a closed device with a condensation system, a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate is used to leaching the rare earth ore (such as Baotou rare earth concentrate), and the mixture is filtered while hot to obtain a first filtrate and leaching residue (also referred to as filter residue);

[0037] Step S2: adding calcium sulfate seed crystals to the first filtrate, stirring for 1-2 hours, allowing calcium sulfate to crystallize rapidly, standing for 1 day or more, and filtering while hot to obtain calcium sulfate crystals and a second filtrate;

[0038] Step S3: adding sodium sulfate to the second filtrate, stirring at a temperature of 20-100° C. (preferably 60-100° C., more preferably 90-100° C.) for 20-50 min, filtering to obtain a third filtrate of a fluorine-containing aluminum complex and a rare earth sulfate double salt having a chemical formula of NaRE(SO4)2, which can be washed with a 5-10% sodium sulfate solution and then dried; and

[0039] Step S4: adding sodium fluoride to the third filtrate, adding a pH regulator to the third filtrate to adjust the pH of the third filtrate to which sodium fluoride has been added to 3-5, stirring at a temperature of 20-100°C (preferably 60-100°C, more preferably 90-100°C) for 50-70 minutes, filtering to obtain cryolite with a chemical formula of Na3AlF6 and a fourth filtrate, and the cryolite can be washed with water and dried.

[0040] In the mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate, the concentration range of the sulfuric acid is 2-3.5 mol / L, specifically 2 mol / L, 2.5 mol / L, 3 mol / L, or 3.5 mol / L; the concentration range of the hydrochloric acid is 0.3-2 mol / L, specifically 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 1.9 mol / L, or 2 mol / L; the concentration range of the aluminum sulfate is 0.15-0.3 mol / L, specifically 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.26 mol / L, or 0.3 mol / L. The equivalent concentration range of sulfuric acid and hydrochloric acid is 6-7mol / L, specifically 6.1mol / L, 6.2mol / L, 6.3mol / L, 6.4mol / L, 6.5mol / L, 6.6mol / L, 6.7mol / L, 6.8mol / L, 6.9mol / L or 7mol / L. It is understandable that when hydrogen ions are completely provided by hydrochloric acid, the concentration of hydrochloric acid needs to be set larger, and the introduction of too many chloride ions will cause the subsequent recovery of rare earths by cumbersome extraction treatment. The concentration of hydrochloric acid of the present invention can be set to be not more than the concentration of sulfuric acid, and the concentration of hydrochloric acid is set smaller, which can not only avoid the extraction operation caused by excessive chloride ion content, but also avoid the subsequent steps S2-S3 of the present invention caused by excessive chloride ion content. Hydrochloric acid, sulfuric acid and aluminum sulfate are used in combination to efficiently leach rare earths, simplify operation, reduce costs and avoid pollution.

[0041] The concentration ratio of the sulfuric acid to the hydrochloric acid is 1-11.7:1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, or 11.7:1. The concentration ratio of the sulfuric acid to the aluminum sulfate is 6.7-23.3:1, specifically 6.7:1, 10:1, 15:1, 20:1, 23:1, or 23.3:1. The concentration ratio of the hydrochloric acid to the aluminum sulfate is 1-13.3:1, specifically 1:1, 2:1, 5:1, 10:1, 12:1, or 13.3:1.

[0042] In the leaching process, the leaching temperature is 120-140°C, the leaching time is 2-3h, the stirring speed is 100-300r / min, and the liquid-solid ratio (i.e., the mass ratio of the mixed solution to the rare earth ore) is 20-44:1. The leaching temperature of the leaching process is relatively low, which can reduce energy loss and save costs. The liquid-solid ratio can specifically be 20:1, 25:1, 30:1, 35:1, 40:1, 42:1, or 44:1. It can be understood that when the liquid-solid ratio is large, it is beneficial to the leaching of fluorocarbon cerium ore, but it will reduce the concentration of rare earths and is not conducive to the recovery of rare earths. The present invention can select a smaller liquid-solid ratio to facilitate the subsequent recovery of rare earth and fluorine aluminum resources while ensuring the leaching rate of fluorocarbon cerium ore, or a larger liquid-solid ratio can be selected to facilitate the leaching of fluorocarbon cerium ore. Specifically, when the liquid-solid ratio is relatively large, fluorocarbon cerium ore can also be fully leached; when hydrochloric acid, sulfuric acid and aluminum sulfate are used in combination, aluminum ions can stabilize fluorine ions in the solution and prevent them from escaping, and can also promote the leaching of fluorocarbon cerium ore. At the same time, with the assistance of aluminum ions, hydrochloric acid and sulfuric acid can leach all or almost all fluorocarbon cerium ore in rare earth ores; after removing calcium ions in the form of crystallized calcium sulfate, sodium sulfate is added. Since aluminum sulfate is added during leaching, the sulfate ion in aluminum sulfate is a necessary condition for the formation of rare earth sulfate double salts. Therefore, the presence of aluminum sulfate makes it easier to form rare earth sulfate double salts and makes the recovery rate of rare earths higher.

[0043] The calcium sulfate seed crystals are calcium sulfate dihydrate and / or calcium sulfate. The calcium sulfate seed crystals are added in an amount of 0.05-0.5% of the mass of the first filtrate, specifically 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0044] The mass ratio of the sodium sulfate to the rare earth oxide in the second filtrate is 2-3:1, specifically 2:1, 2.5:1, or 3:1.

[0045] The fourth filtrate can obtain sodium sulfate after concentration and crystallization. After filtering out the sodium sulfate, the fourth filtrate mainly contains the remaining fluoride ions, the sulfate ions that have not been completely precipitated, the chloride ions, and the sodium ions, and can continue to be configured as a mixed solution for re-leaching, and the remaining fluoride ions do not affect the continued leaching, while the presence of sulfate ions and a small amount of chloride ions is beneficial to the leaching. The combination of hydrochloric acid, sulfuric acid and aluminum sulfate still has a high rare earth leaching rate even if other ions remain in the fourth filtrate.

[0046] The amount of sodium fluoride added is 5-7 times the concentration of aluminum ions in the third filtrate, specifically 5 times, 6 times, or 7 times.

[0047] The pH adjusting agent may be at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide. The pH adjusting agent may be added to the third filtrate in the form of a solution. In one embodiment, a sodium carbonate solution is added to the third filtrate, and the concentration of sodium carbonate is 2-3 mol / L.

[0048] Rare earth sulfate double salt can be converted by alkali (i.e., adding sodium hydroxide to the rare earth sulfate double salt solution) to obtain rare earth hydroxide after impurities are removed. The rare earth hydroxide reacts with an acid such as hydrochloric acid to obtain a rare earth chloride solution.

[0049] The rare earth ore can be Baotou rare earth concentrate or other rare earth concentrates, the content of bastnaesite in the rare earth ore is not less than 50%, and the mesh size of the rare earth ore is above 200 meshes.

[0050] In the technical solution of the present invention, a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate is used to leach the rare earth ore, and the mixture is filtered to obtain a first filtrate. The aluminum ions in the aluminum sulfate can not only promote the separation of fluorocarbon cerium ore and monazite, but also fully complex with the fluorine ions in the leaching solution to form a soluble complex, stabilize the fluorine in the filtrate, and avoid the fluorine ions from escaping to form hydrogen fluoride and polluting the environment. With the assistance of aluminum sulfate, the hydrogen ions provided by sulfuric acid and hydrochloric acid can separate all or almost all of the fluorocarbon cerium ore from monazite in the rare earth ore to obtain a first filtrate and a monazite filter residue. First, monazite is separated from fluorocarbon cerium ore to avoid fluorocarbon cerium ore affecting the post-treatment of monazite, which is conducive to obtaining high-purity trisodium phosphate by alkaline decomposition. The cooperation of sulfuric acid, hydrochloric acid and aluminum sulfate can not only achieve a higher rare earth leaching rate (the leaching rate of fluorocarbon cerium ore is not less than 97%), but also stabilize the fluorine ions in the filtrate to prevent the fluorine ions from escaping and polluting the environment, and can also save the step of recovering rare earths by extraction due to excessive addition of hydrochloric acid. Calcium sulfate seeds are added to the first filtrate to generate calcium sulfate crystal precipitation to recover calcium, so as to remove most of the calcium ions in the first filtrate and obtain the second filtrate. Sodium sulfate is added to the second filtrate, heated and reacted, and filtered to obtain the third filtrate and rare earth sulfate complex salt (chemical formula is NaRE (SO4) 2), and rare earths are recovered in the form of complex salt. Sodium fluoride is added to the third filtrate, the pH is 3-5, heated and reacted, and filtered to obtain cryolite (chemical formula is Na3AlF6) to recover aluminum fluoride, which can prevent the generation of fluorine waste gas. The method of the present invention for recovering rare earth and fluorine-aluminum by aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching of rare earth ores does not require high-temperature treatment, is simple to operate, can be produced continuously, has a high rare earth recovery rate, and does not generate pollutants such as radioactive waste residues, hydrogen fluoride or nitrogen wastewater. Under the premise of ensuring the rare earth leaching rate, the rare earth and aluminum-fluoride in the rare earth ores are recovered at a lower cost and in a greener and more environmentally friendly manner (nearly zero emission).

[0051] Furthermore, the monazite leaching residue can be subjected to alkaline decomposition treatment. The fluorine concentration in the monazite (the fluorine ion concentration in the monazite residue after acid decomposition is about 0.5-0.6%, while the rare earth ore before leaching contains about 9.5-10% fluorine) is very low and will not affect the purity of trisodium phosphate. The solution separated by alkali conversion can be used to prepare trisodium phosphate, and the remaining sodium hydroxide solution can be further recycled to leach monazite.

[0052] Embodiment 1

[0053] Weigh 500g of Baotou mixed rare earth concentrate with a total rare earth oxide content of 53% in a closed device with a condensation system. The leaching conditions are: equivalent H + The concentration is 7 mol / L, the ratio of sulfuric acid to hydrochloric acid is 2.5:1, the concentration of aluminum sulfate is 0.25 mol / L, the reaction temperature is 135°C, the liquid-solid ratio is 42:1, the reaction time is 3h, and the stirring speed is 200r / min. Under these conditions, after the reaction, the first filtrate is filtered while hot to obtain the first filtrate, and the leaching residue mainly composed of monazite is washed and dried; 0.1% calcium sulfate seed is added to the first filtrate for decalcification, and the total content of impurities rare earth and aluminum in the obtained calcium sulfate crystal precipitate is not higher than 1%, and the second filtrate is obtained by filtering; sodium sulfate is added to the second filtrate, the mass ratio of Na2SO4 to RE2O3 is 2.5:1, and the mixture is stirred at a temperature of 90°C for 30 minutes, and filtered while hot to obtain rare earth sulfate double salt and a third filtrate, and the rare earth sulfate double salt is washed with a 5% sodium sulfate solution and then dried; NaF is added to the third filtrate, and the pH is adjusted to 3 with Na2CO3 to prepare cryolite. The leaching rate of bastnaesite was measured and calculated by the ammonium ferrous sulfate cerium volumetric method, and the leaching rate of bastnaesite was 97%. The rare earth concentration in the second filtrate was measured by ICP-MS, and the rare earth recovery rate was 95.5%. The aluminum yield was about 99%, and the fluorine yield was about 48%.

[0054] Comparative Example 1

[0055] Comparative Example 1 was carried out according to Example 1. The differences between Comparative Example 1 and Example 1 include: using H + Leaching of ore with H2SO4-HCl at a concentration of 7 mol / L.

[0056] Comparative Example 2

[0057] Comparative Example 2 was carried out according to Example 1. The differences between Comparative Example 2 and Example 1 include: using H + The ore was leached with 7 mol / L H2SO4-HCl and 0.05 mol / L Al2(SO4)3.

[0058] Embodiment 2

[0059] Embodiment 2 is carried out according to Embodiment 1. The differences between Embodiment 2 and Embodiment 1 include: using H + The ore was leached with 7 mol / L H2SO4-HCl and 0.15 mol / L Al2(SO4)3.

[0060] Fluoride ions overflowing from Comparative Examples 1 to 2 and Example 2 were absorbed with 0.5 mol / L NaOH solution, and the fluoride ion content in the absorption solution was measured every 15 minutes. Figure 3 As shown, it can be clearly seen that in the reaction with the participation of aluminum salt, the concentration of fluoride ions in the absorption liquid decreases sharply, indicating that aluminum salt can effectively fix fluoride ions in the solution, thereby inhibiting the escape of hydrogen fluoride, but the concentration of aluminum salt added needs to be sufficient.

[0061] Comparative Example 3

[0062] Comparative Example 3 was carried out according to Example 1. The differences between Comparative Example 3 and Example 1 include: 0.3 mol / L Al2(SO4)3 was used for leaching, the liquid-solid ratio was 32:1, and the reaction time was 2 h.

[0063] Embodiment 3

[0064] Embodiment 3 is carried out according to Embodiment 1. The differences between Embodiment 3 and Embodiment 1 include: using H + The concentration of 6 mol / L H2SO4-HCl and 0.3 mol / L Al2(SO4)3 was used for leaching, the liquid-solid ratio was 32:1, and the reaction time was 2h. Among them, the ratio of c(H2SO4) to c(HCl) can be set to 11:1, 8:1, 5:1, and 2:1.

[0065] like Figure 4 As shown in the figure, the rare earth leaching rate increases first and then levels off with the increase of the ratio of sulfate acid equivalent concentration.

[0066] Embodiment 4

[0067] Example 4 was carried out according to Example 1. The differences between Example 4 and Example 1 include: using H2SO4-HCl and 0.3 mol / L Al2(SO4)3 to leaching ore, liquid-solid ratio of 32:1, reaction time of 2h. + The concentration can be set to 4mol / L, 5mol / L, 6mol / L, 7mol / L, and 8mol / L.

[0068] like Figure 5 As shown, in H + When the concentration is 4-8 mol / L, the rare earth leaching rate continues to rise with the increase of hydrogen ion concentration, but when it is greater than 7 mol / L, the reaction is too intense and calcium sulfate will precipitate prematurely, which is not conducive to the subsequent separation of monazite.

[0069] Embodiment 5

[0070] Embodiment 5 is carried out according to Embodiment 1. The differences between Embodiment 5 and Embodiment 1 include: using H + The concentration of 7 mol / L H2SO4-HCl and Al2(SO4)3 was used for leaching, the liquid-solid ratio was 32:1, and the reaction time was 2h. Among them, the ratio of c(H2SO4) to c(HCl) can be set to 5:1, and the concentration of Al2(SO4)3 can be set to 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, and 0.35 mol / L.

[0071] like Figure 6 As shown, when the concentration of Al2(SO4)3 is 0.15-0.35 mol / L, the rare earth leaching rate increases first and then decreases with the increase of Al2(SO4)3 concentration.

[0072] Embodiment 6

[0073] Embodiment 6 is carried out according to Embodiment 1. The differences between Embodiment 6 and Embodiment 1 include: using H + The concentration of 7 mol / L H2SO4-HCl and 0.25 mol / L Al2(SO4)3 is used for leaching, the liquid-solid ratio is 32:1, and the reaction time is 2 hours. Among them, the ratio of c(H2SO4) to c(HCl) can be set to 5:1, and the leaching reaction temperature can be set to 110℃, 120℃, 130℃, 135℃, and 140℃.

[0074] like Figure 7 As shown, when the leaching reaction temperature is 110-140°C, the rare earth leaching rate first increases and then decreases with the increase of temperature.

[0075] Embodiment 7

[0076] Embodiment 7 is carried out according to Embodiment 1. The differences between Embodiment 7 and Embodiment 1 include: using H + The concentration of 7 mol / L H2SO4-HCl and 0.25 mol / L Al2(SO4)3 was used for leaching, and the reaction time was 2 hours. The ratio of c(H2SO4) to c(HCl) can be set to 5:1, and the liquid-solid ratio can be set to 28:1, 32:1, 36:1, 40:1, 42:1, 44:1.

[0077] like Figure 8 As shown, when the liquid-to-solid ratio is 28-44:1, as the reaction liquid-to-solid ratio increases, the rare earth leaching rate continues to increase, and after reaching 42:1, the growth rate slows down.

[0078] Embodiment 8

[0079] Embodiment 8 is carried out according to Embodiment 1. The differences between Embodiment 8 and Embodiment 1 include: using H + The concentration of 7 mol / L H2SO4-HCl and 0.25 mol / L Al2(SO4)3 is used for leaching, and the reaction time is 2 hours. Among them, the ratio of c(H2SO4) to c(HCl) can be set to 5:1, and the leaching reaction time can be set to 1.5h, 2h, 2.5h, 3h, and 3.5h.

[0080] like Fig. 9 As shown, when the leaching reaction time is 1.5-3.5h, the rare earth leaching rate increases with the extension of the leaching reaction time, and the growth rate slows down after the reaction time is greater than 3.0h.

[0081] Embodiment 9

[0082] Example 9 was carried out according to Example 1. The difference between Example 9 and Example 1 is that sodium sulfate was added to the second filtrate and stirred at 20° C. for 30 minutes. The mass ratio of Na2SO4 to RE2O3 was 1:1, 1.5:1, 2:1, 2.5:1, and 3:1.

[0083] like Fig.10 As shown, when the mass ratio of Na2SO4 to RE2O3 is 1:1-3:1, as the mass ratio of Na2SO4 to RE2O3 increases, the rare earth recovery first increases and then tends to be flat.

[0084] Embodiment 10

[0085] According to Example 1, Example 10 is carried out, and the difference between Example 10 and Example 1 includes: sodium sulfate is added to the second filtrate, and the reaction is carried out at a temperature of 20° C. The reaction time can be set to 10 min, 20 min, 30 min, 40 min, or 50 min.

[0086] like Fig.11 As shown, when the reaction time is 10-50 min, as the reaction time increases, the rare earth recovery rate first increases and then tends to be flat. After the reaction time is 30 min, the rare earth recovery rate remains basically unchanged.

[0087] Embodiment 11

[0088] According to Example 1, Example 11 is carried out, and the difference between Example 11 and Example 1 includes: sodium sulfate is added to the second filtrate, and the reaction is carried out for 30 minutes. The reaction temperature can be set to 20°C, 50°C, 70°C, 90°C, or 100°C.

[0089] like Fig.12As shown, when the reaction temperature is 20-100°C, as the reaction temperature increases, the rare earth recovery rate first increases and then tends to be flat. After the reaction temperature increases to 90°C, the rare earth recovery rate remains basically unchanged.

[0090] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching, comprising the following steps: The rare earth ore is leached with a mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate, and filtered to obtain a first filtrate; Add calcium sulfate seed crystals to the first filtrate, filter, and obtain calcium sulfate crystals and a second filtrate; adding sodium sulfate to the second filtrate, filtering, and obtaining a third filtrate and rare earth sulfate double salt; and Sodium fluoride is added to the third filtrate, and a pH regulator is added to adjust the pH to 3-5, and the mixture is filtered to obtain cryolite.

2. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: In the mixed solution containing sulfuric acid, hydrochloric acid and aluminum sulfate, the concentration range of the sulfuric acid is 2-3.5 mol / L, the concentration range of the hydrochloric acid is 0.3-2 mol / L, and the concentration range of the aluminum sulfate is 0.15-0.3 mol / L.

3. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: In the leaching process, the leaching temperature is 120-140° C., the leaching time is 2-3 hours, the stirring speed is 100-300 r / min, and the liquid-solid ratio is 20-44:

1.

4. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: The calcium sulfate seed crystals are calcium sulfate dihydrate and / or calcium sulfate, and the added amount of the calcium sulfate seed crystals is 0.05-0.5% of the mass of the first filtrate.

5. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: The step of "adding sodium sulfate to the second filtrate" includes: adding sodium sulfate to the second filtrate at a temperature of 20-100°C and stirring for 20-50 minutes, wherein the mass ratio of the sodium sulfate to the rare earth oxide in the second filtrate is 2-3:

1.

6. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: The amount of sodium fluoride added is 5-7 times the aluminum ion concentration in the third filtrate.

7. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: The pH adjuster is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

8. The method for recovering rare earth and fluorine aluminum from rare earth ores by using aluminum salt-assisted sulfuric acid and hydrochloric acid mixed enhanced leaching according to claim 1, characterized in that: In the step of "adding sodium fluoride to the third filtrate, filtering, and obtaining cryolite", the heating reaction is stirring at a temperature of 20-100° C. for 50-70 minutes.

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