Method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate

Abstract

The present invention provides a method for recovering rare earths, aluminum and fluorine by using aluminum sulfate to assist sulfuric acid in leaching rare earth ores, which comprises the following steps: leaching rare earth ores with a mixed solution containing sulfuric acid and aluminum sulfate, and filtering to obtain a first filtrate; adding calcium sulfate seeds to the first filtrate, and filtering to obtain calcium sulfate crystals and a second filtrate; performing a first extraction treatment on the second filtrate to obtain a first raffinate and a first organic phase; performing a first stripping treatment on the first organic phase to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid; performing a second extraction treatment on the first raffinate to obtain a second raffinate and a second organic phase; performing a second stripping treatment on the second organic phase to obtain a mixed solution containing rare earth ions; adding sodium fluoride to the second raffinate, and adding a pH regulator to adjust the pH to 3-5, and filtering to obtain cryolite. The method for recovering rare earths, aluminum and fluorine by using aluminum sulfate to assist sulfuric acid in leaching rare earth ores of the present invention has a high rare earth leaching rate, lower cost and more environmentally friendly effect.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth hydrometallurgy, and particularly to a method for recovering rare earth, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate. Background Art

[0002] Baotou rare earth concentrate is a mixture of bastnasite and monazite, and their chemical properties are inconsistent, making the decomposition and separation technology difficult. At present, the acid method and the alkali method are usually used in industry to treat Baotou rare earth concentrate. The most representative ones are the concentrated sulfuric acid high-temperature roasting method and the caustic soda decomposition method. Among them, more than 90% of the rare earth concentrate is treated by the concentrated sulfuric acid high-temperature roasting method. The concentrated sulfuric acid high-temperature roasting method has the advantages of simple operation, continuous production, and high rare earth recovery rate. However, the concentrated sulfuric acid high-temperature roasting method also has many disadvantages, such as high roasting temperature, large amount of radioactive waste residue, formation of a large amount of high-temperature waste gas (such as HF, SiF4, SO3, etc.), requiring a large amount of water for cooling and absorbing waste gas, difficult recovery of the formed mixed acid, and high recovery cost. The caustic soda decomposition method is a relatively environmentally friendly process, and also has the advantages of not generating harmful gases during the production process, small amount of waste residue, and the recoverability of sodium fluoride and sodium phosphate in wastewater. However, the caustic soda decomposition method generally requires the grade of rare earth concentrate to be above 55% (that is, the content of bastnasite in the rare earth concentrate is not less than 55%), and special chemical beneficiation methods are required to remove calcium. In addition, the caustic soda decomposition method has the disadvantages of generating a large amount of wastewater, long mineral decomposition time, discontinuous production process, large amount of NaOH used, and high cost, thus restricting the large-scale application of the caustic soda decomposition method.

[0003] With the development of society, the requirements for environmental protection in the production process are becoming more and more strict. Therefore, there is an urgent need to develop new processes to achieve the purpose of recovering rare earth and associated resources in rare earth concentrate with lower cost and green environmental protection on the premise of ensuring the rare earth leaching rate.

[0004] Application Content

[0005] In view of the above defects of the prior art, the present invention provides a method for recovering rare earth, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate, aiming to recover rare earth and associated resources in rare earth ore with lower cost and more green environmental protection on the premise of ensuring the rare earth leaching rate.

[0006] The method for recovering rare earth, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate provided by the present invention includes the following steps:

[0007] Adding calcium sulfate seeds to the first filtrate, filtering to obtain calcium sulfate crystals and a second filtrate;

[0008] Performing a first extraction treatment on the second filtrate to obtain a first raffinate and a first organic phase;

[0009] Perform a first back-extraction treatment on the first organic phase to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid;

[0010] Perform a second extraction treatment on the first raffinate to obtain a second raffinate and a second organic phase;

[0011] Perform a second back-extraction treatment on the second organic phase to obtain a mixed solution containing rare earth ions; and

[0012] Add sodium fluoride to the second raffinate, add a pH regulator to adjust the pH to 3 - 5, and filter to obtain cryolite.

[0013] Furthermore, in the mixed solution containing sulfuric acid and aluminum sulfate, the concentration range of sulfuric acid is 1.5 - 3.5 mol / L, and the concentration range of aluminum sulfate is 0.15 - 0.50 mol / L.

[0014] Furthermore, in the leaching treatment, the leaching temperature is 120 - 140 °C, the leaching time is 0.5 - 2.5 h, the stirring speed is 150 - 250 r / min, and the liquid - solid ratio is 10 - 40:1.

[0015] Furthermore, at least one of the following conditions is satisfied:

[0016] In the rare earth ore, the mineral particles are not less than 100 mesh;

[0017] In the rare earth ore, the content of bastnasite is not less than 50%;

[0018] The calcium sulfate seed crystal is calcium sulfate dihydrate and / or calcium sulfate;

[0019] The addition amount of the calcium sulfate seed crystal is 0.05 - 0.5% of the mass of the first filtrate;

[0020] The addition amount of sodium fluoride is 5 - 7 times the concentration of aluminum ions in the second raffinate;

[0021] In the first back - extraction treatment, the back - extractant is water and / or the filtrate obtained by filtration during the preparation of cryolite;

[0022] In the first extraction treatment, the extractant is tri - iso - octylamine, the phase ratio is 0.5 - 4, the oscillation time is 5 - 30 min, and the extraction temperature is room temperature;

[0023] In the second extraction treatment, the extractant is secondary carbon primary amine, the phase ratio is 0.5 - 4, the oscillation time is 5 - 30 min, and the extraction temperature is room temperature.

[0024] Further, in the second stripping treatment, the concentration range of the stripping agent in the stripping solution is 1-6 mol / L, the stripping agent is at least one of hydrochloric acid, ammonium chloride, and magnesium chloride, and the rare earth ion-containing mixed solution contains rare earth chloride.

[0025] Further, before the step of "performing a second stripping treatment on the second organic phase", the method for recovering rare earth and aluminum fluoride by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate further includes:

[0026] Washing the second organic phase with a backwashing solution having a concentration of 0.01-0.5 mol / L, wherein the backwashing solution includes a sulfuric acid solution and / or an ammonium sulfate solution, and the phase ratio is 1-3. The rare earth ion-containing mixed solution contains rare earth sulfate and rare earth chloride.

[0027] Further, the method for recovering rare earth and aluminum fluoride by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate further includes the following steps:

[0028] Adding at least one of sodium carbonate, sodium bicarbonate, and ammonium bicarbonate to the rare earth ion-containing mixed solution, and filtering to obtain a rare earth precipitate.

[0029] Further, the pH regulator is at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide.

[0030] Further, in the step of "adding sodium fluoride to the second raffinate, filtering to obtain cryolite", the reaction temperature is 20-100 °C, and the reaction time is 20-70 min.

[0031] In the technical solution of the present invention, a mixed solution containing sulfuric acid and aluminum sulfate is used to leach rare earth ores, and a first filtrate is obtained after filtration. The aluminum ions in aluminum sulfate can not only promote the separation of bastnasite and monazite, but also fully complex with fluoride ions in the leaching solution to form soluble complexes, stabilizing fluorine in the first filtrate and preventing fluoride ions from escaping as hydrogen fluoride and polluting the environment. With the assistance of aluminum sulfate, the hydrogen ions provided by sulfuric acid can separate all or almost all of the bastnasite from monazite in the rare earth ore, obtaining a first filtrate and a monazite filter residue. Separating monazite from bastnasite first can avoid the influence of bastnasite on the post-treatment of monazite and is conducive to obtaining high-purity trisodium phosphate through alkaline decomposition. Sulfuric acid and aluminum sulfate cooperate with each other, not only achieving a relatively high rare earth leaching rate (the leaching rate of bastnasite is not less than 97%), but also stabilizing fluoride ions in the filtrate to prevent fluoride ions from escaping and polluting the environment. Calcium sulfate seeds are added to the first filtrate to generate calcium sulfate crystal precipitates to recover calcium, removing all or almost all of the calcium ions in the first filtrate to obtain a second filtrate. The second filtrate is subjected to a first extraction treatment to obtain a first raffinate and a first organic phase. The first organic phase is subjected to a first stripping treatment to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid to recover part of the fluorine, and the recovered sulfuric acid can be reused for ore leaching to save costs. The first raffinate is subjected to a second extraction treatment to obtain a second raffinate and a second organic phase. The second organic phase is subjected to a second stripping treatment to obtain a mixed solution containing rare earth ions to recover rare earth. Sodium fluoride is added to the second raffinate, and a pH regulator is added to adjust the pH to 3-5, followed by filtration to obtain cryolite (chemical structural formula: Na3AlF6) to recover the remaining fluorine and aluminum. The method for recovering rare earth, aluminum, and fluorine by sulfuric acid-assisted sulfuric acid leaching of rare earth ores of the present invention does not require high-temperature treatment, has simple operation, can be continuously produced, has a high rare earth recovery rate, low energy consumption, does not generate radioactive waste residues, high-temperature waste gases (such as HF, SiF4, SO3, etc.) or nitrogen-containing wastewater and other pollutants, and recovers rare earth, aluminum, and fluorine in rare earth ores at a lower cost and in a more environmentally friendly manner (almost zero emissions) on the premise of ensuring the rare earth leaching rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the solution of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a process flow diagram of the method for recovering rare earth, aluminum, and fluorine by sulfuric acid-assisted sulfuric acid leaching of rare earth ores according to an embodiment of the present invention.

[0034] Figure 2It is a process flow diagram of a method for recovering rare earths, aluminum, and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to a specific embodiment of the present invention.

[0035] Figure 3 It is a comparative curve graph of the overflow of fluoride ions over time in Comparative Example 1 and Example 1.

[0036] Figure 4 It is a graph showing the effect of sulfuric acid concentration on the rare earth leaching rate.

[0037] Figure 5 It is a graph showing the effect of aluminum sulfate concentration on the rare earth leaching rate.

[0038] Figure 6 It is a graph showing the effect of liquid-solid ratio on the rare earth leaching rate.

[0039] Figure 7 It is a graph showing the effect of leaching reaction temperature on the rare earth leaching rate.

[0040] Figure 8 It is a graph showing the effect of leaching reaction time on the rare earth leaching rate.

[0041] Figure 9 It is a graph showing the relationship between the initial pH value of the second leaching solution and the extraction rate of primary amine rare earth.

[0042] Figure 10 It is a graph showing the relationship between the primary amine phase ratio and the extraction rates of rare earth ions and aluminum ions in the leaching solution.

[0043] Figure 11 It is a graph showing the relationship between the extraction rates of various ions in the second leaching solution with and without triisooctylamine and the triisooctylamine phase ratio.

[0044] Figure 12 It is a graph showing the relationship between the extraction rates of unprotonated primary amine with and without triisooctylamine and the triisooctylamine phase ratio.

[0045] Figure 13 It is a graph showing the effect of ammonium sulfate concentration on the backwashing of aluminum ions.

[0046] Figure 14 It is an effect diagram of back-extracting the primary amine organic phase with different chloride solutions.

[0047] The realization, functional characteristics, and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed Embodiments

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work shall fall within the scope of protection of the present invention.

[0049] In the present invention, the descriptions involving "first", "second", etc. are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments may be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0050] Refer Figure 1-2 , an embodiment of the present invention provides a method for recovering rare earths and aluminum fluoride by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate, comprising the following steps:

[0051] Step S1: In a closed device with a condensation system, leach the rare earth ore with a mixed solution containing sulfuric acid and aluminum sulfate, filter while it is hot to obtain a first filtrate and a leaching residue mainly composed of monazite (which can also be called a filter residue), and the leaching residue can be rinsed with water 2 - 4 times;

[0052] Step S2: Add calcium sulfate seeds to the first filtrate, stir for 1 - 2 h, calcium sulfate crystallizes rapidly, stand for 1 day or more, and then filter to obtain calcium sulfate crystals and a second filtrate;

[0053] Step S3: At room temperature, perform a first extraction treatment on the second filtrate with triisooctylamine to obtain a first raffinate and a first organic phase, wherein the phase ratio (O / A) is 0.5 - 4, and the oscillation time is 5 - 30 min;

[0054] Step S4: Perform a first stripping treatment on the first organic phase with water and / or the third filtrate obtained in Step S7 to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid. The mixed acid solution containing hydrofluoric acid and sulfuric acid can be subjected to distillation treatment to obtain sulfuric acid solution and hydrofluoric acid, and the sulfuric acid solution can be continuously used to prepare the mixed solution for leaching treatment;

[0055] Step S5: At room temperature, perform a second extraction treatment on the first raffinate with protonated or unprotonated secondary carbon primary amine (such as primary amine of model N1923) to obtain a second raffinate containing fluorine - aluminum and a second organic phase containing rare earths, wherein the phase ratio (O / A) is 0.5 - 4, and the oscillation time is 5 - 30 min;

[0056] Step S6: Perform a second stripping treatment on the second organic phase with at least one of hydrochloric acid, ammonium chloride, and magnesium chloride to obtain a mixed solution containing rare earth ions, wherein the mixed solution contains rare earth chlorides; and

[0057] Step S7: Add sodium fluoride to the second raffinate, then add a pH regulator to adjust the pH to 3 - 5, react at a temperature of 20 - 100 °C for 20 - 70 min, and filter to obtain a third filtrate and cryolite (chemical structural formula: Na3AlF6).

[0058] The rare earth ore can be Baotou rare earth concentrate or rare earth concentrate containing bastnasite from other production areas. In the rare earth ore, the content of bastnasite is not less than 50% (i.e., the content of rare earth oxides is not less than 50%), and the concentrate particles are not less than 100 mesh.

[0059] In the mixed solution containing sulfuric acid and aluminum sulfate, the concentration range of sulfuric acid is 1.5 - 3.5 mol / L, specifically it can be 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or 3.5 mol / L; the concentration range of aluminum sulfate is 0.15 - 0.50 mol / L, specifically it can be 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, or 0.5 mol / L. The concentration ratio of sulfuric acid to aluminum sulfate can be 3 - 23.3:1, specifically it can be 3:1, 5:1, 10:1, 15:1, 20:1, 23:1, or 23.3:1. In the mixed solution containing sulfuric acid and aluminum sulfate, hydrogen ions can be in excess to ensure that all or almost all of the bastnasite in the rare earth ore is leached. At the same time, the excess acid can be recycled in step S4; aluminum ions can also be in excess to ensure that fluoride ions are completely or nearly completely stabilized in the first filtrate. At the same time, the excess aluminum ions can be recycled in step S7. The combined use of sulfuric acid and aluminum sulfate can efficiently leach rare earths and avoid pollution.

[0060] In the leaching treatment, the leaching temperature is 120 - 140 °C, the leaching time is 0.5 - 2.5 h, the stirring speed is 150 - 250 r / min, and the liquid-solid ratio (i.e., the mass ratio of the mixed solution to the rare earth ore) is 10 - 40:1. The liquid-solid ratio can specifically be 10:1, 15:1, 20:1, 25:1, 30:1, 32:1, 34:1, 36:1, 38:1, or 40:1. It can be understood that when the liquid-solid ratio is large, it is beneficial to the leaching of bastnasite, but it will reduce the concentration of rare earths and is not conducive to the recovery of rare earths. In the present invention, a smaller liquid-solid ratio can be selected to facilitate the subsequent recovery of rare earth and fluorine-aluminum resources while ensuring the leaching rate of bastnasite, or a larger liquid-solid ratio can be selected to facilitate the leaching of bastnasite. Specifically, when the liquid-solid ratio is large, bastnasite can also be fully leached; when sulfuric acid and aluminum sulfate are used in combination, aluminum ions can stabilize fluoride ions in the solution without escaping, and can also promote the leaching of bastnasite. At the same time, with the assistance of aluminum ions, sulfuric acid can leach all or almost all of the bastnasite in the rare earth ore; a mixture containing rare earth ions is obtained through multiple extraction and back-extraction treatments to recover rare earths. The mixed solution containing rare earth ions contains rare earth sulfate, and the sulfate radical in aluminum sulfate is a necessary condition for the formation of rare earth sulfate double salts. The presence of aluminum sulfate makes it easier to form rare earth sulfate double salts and results in a higher recovery rate of rare earths.

[0061] The calcium sulfate seed crystal is calcium sulfate dihydrate and / or calcium sulfate. The addition amount of the calcium sulfate seed crystal is 0.05 - 0.5% of the mass of the first filtrate, and can specifically be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. The amount of rare earth oxide contained in the obtained CaSO₄·2H₂O crystal precipitate is not more than 0.78%, indicating that calcium and rare earths are almost completely separated.

[0062] The first extraction treatment and the second extraction treatment are carried out in the form of horizontal oscillation on a speed-regulating multi-purpose oscillator.

[0063] Before the second back-extraction treatment of the second organic phase, the method for recovering rare earth and aluminum fluoride by using aluminum sulfate to assist sulfuric acid in leaching rare earth ore further includes: back-washing the second organic phase with a back-washing solution of 0.01 - 0.5 mol / L. At this time, the mixed solution containing rare earth ions contains rare earth sulfate and rare earth chloride. The back-washing solution includes sulfuric acid solution and / or ammonium sulfate solution, and the phase ratio can be 1 - 3, specifically 1, 2, or 3. When the back-washing solution is ammonium sulfate solution, the mass percentage content of ammonium sulfate is 1 - 7%, specifically 1%, 2%, 3%, 4%, 5%, 6%, or 7%. When the back-washing solution is sulfuric acid solution, the concentration is preferably 0.01 - 0.5 mol / L. In the mixed solution containing rare earth ions, c Al / c RENot greater than 0.008, indicating that aluminum and rare earths are almost completely separated.

[0064] In the second stripping treatment, the concentration range of the stripping agent in the stripping solution is 1-6 mol / L, and specifically can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or 6 mol / L.

[0065] The mixed acid solution containing hydrofluoric acid and sulfuric acid is subjected to distillation treatment to obtain a sulfuric acid solution and hydrofluoric acid. In the mixed acid solution, the molar ratio of H2SO4 to HF is 30-45:1, which indicates that the addition of sulfuric acid is in excess to separate all or almost all of the bastnasite and monazite in the rare earth ore. After the distillation treatment, the excess sulfuric acid can be recovered and reused to avoid waste. The molar ratio of H2SO4 to HF can specifically be 30:1, 32:1, 35:1, 40:1, 42:1, or 45:1. The pH of the second filtrate is 0-2, and the pH can specifically be 0, 0.5, 1, 1.5, or 2.

[0066] The method for recovering rare earths and aluminum fluoride by using aluminum sulfate to assist in the sulfuric acid leaching of rare earth ore further includes the following steps: adding at least one of sodium carbonate, sodium bicarbonate, and ammonium bicarbonate to the mixed solution containing rare earth ions, and filtering to obtain rare earth precipitate.

[0067] The addition amount (mass) of sodium fluoride is 5-7 times the concentration of aluminum ions in the second raffinate containing fluorine and aluminum, and specifically can be 5 times, 6 times, or 7 times.

[0068] The pH regulator can be at least one of sodium carbonate, sodium bicarbonate, and sodium hydroxide. The pH regulator can 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.

[0069] In the technical solution of the present invention, a mixed solution containing sulfuric acid and aluminum sulfate is used to leach rare earth ore. After filtration, a first filtrate is obtained, which is a strong acid high-aluminum leaching solution rich in rare earths. The aluminum ions in aluminum sulfate can not only promote the separation of bastnasite and monazite, but also fully complex with fluoride ions in the leaching solution to form soluble complexes, stabilizing fluorine in the first filtrate and preventing fluoride ions from forming hydrogen fluoride and escaping to pollute the environment. With the assistance of aluminum sulfate, the hydrogen ions provided by sulfuric acid can separate all or almost all of the bastnasite and monazite in the rare earth ore, obtaining a first filtrate and a monazite filter residue. Separating monazite from bastnasite first can avoid the influence of bastnasite on the post-treatment of monazite, which is beneficial to obtaining high-purity trisodium phosphate through alkaline decomposition. Sulfuric acid and aluminum sulfate cooperate with each other, which can not only achieve a relatively high rare earth leaching rate (the leaching rate of bastnasite is not less than 97%), but also stabilize fluoride ions in the filtrate to prevent fluoride ions from escaping and polluting the environment. Adding calcium sulfate seeds to the first filtrate to form calcium sulfate crystal precipitation to recover calcium, removing all or almost all of the calcium ions in the first filtrate to obtain a second filtrate. Conducting the first extraction treatment on the second filtrate to obtain a first raffinate and a first organic phase, and conducting the first stripping treatment on the first organic phase to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid to recover part of the fluorine. The recovered sulfuric acid can be reused for ore leaching to save costs. Conducting the second extraction treatment on the first raffinate to obtain a second raffinate and a second organic phase. Primary amine has a strong ability to extract and separate rare earths from aluminum, and can completely or almost completely separate aluminum and rare earths. Conducting the second stripping treatment on the second organic phase to obtain a mixed solution containing rare earth ions to recover rare earths. First, triisooctylamine is used to recover acid, and then primary amine is used to extract rare earths. After the organic phase is stripped with extraction agents such as hydrochloric acid, a mixed solution of rare earth chloride with relatively high purity can be obtained. Adding sodium fluoride to the second raffinate and filtering to obtain cryolite (chemical structural formula: Na3AlF6) to recover the remaining fluorine and aluminum, eliminating the generation of fluorine waste gas. The method for recovering rare earths, aluminum, and fluorine from rare earth ore by sulfuric acid leaching assisted by aluminum sulfate in the present invention does not require high-temperature treatment, has simple operation, can be continuously produced, has a high rare earth recovery rate, low energy consumption, does not generate radioactive waste residues, high-temperature waste gases (such as HF, SiF4, SO3, etc.) or nitrogen-containing wastewater and other pollutants. On the premise of ensuring the rare earth leaching rate, it recovers rare earths, aluminum, and fluorine in rare earth ore at a lower cost and in a more environmentally friendly manner (almost zero emissions). After detection, the leaching rate of bastnasite is not less than 85.37%, the extraction rate of rare earths is not less than 97.38%, the stripping rate of rare earths is not less than 98.05%, and the recovery rate of aluminum ions is not less than 98.4%.

[0070] Example 1

[0071] Weigh 1 kg of Baotou rare earth concentrate with a particle size above 100 mesh. The content of rare earth oxides in the Baotou rare earth concentrate is 51.67%. In a closed device with a condensation system, leach the Baotou rare earth concentrate. Among them, the concentration of H2SO4 is 3 mol / L, the concentration of Al2(SO4)3 is 0.30 mol / L, the leaching reaction temperature is 135 °C, the liquid-solid ratio is 32:1, the leaching reaction time is 2 h, and the stirring speed is 200 r / min. After the reaction under these conditions, filter to obtain the first filtrate and the leached residue, and wash the leached residue 3 times with water; add calcium sulfate dihydrate seeds to the first filtrate, perform desulfation treatment on the first filtrate, and filter to obtain the second filtrate; at room temperature, perform the first extraction treatment on the second filtrate in the form of horizontal oscillation on a variable-speed multi-purpose oscillator to obtain the first raffinate and the first organic phase. Among them, the extractant is triisooctylamine, the phase ratio is 2, the oscillation frequency is 200 r / min, and the extraction time is 10 min; the acid in the first organic phase is back-extracted with pure water to obtain a mixed acid (containing sulfuric acid and hydrofluoric acid); perform the second extraction treatment on the first raffinate in the form of horizontal oscillation on a variable-speed multi-purpose oscillator to obtain the second raffinate containing fluorine and aluminum and the second organic phase containing rare earths. Among them, the extractant is primary amine, and the phase ratio is 2; the rare earths in the second organic phase containing rare earths are back-extracted with hydrochloric acid, and the concentration of hydrochloric acid is 2 mol / L. The aluminum ions and rare earth ions in the aqueous phase before and after extraction are measured and calculated by ICP. The second raffinate is made into cryolite by adding NaF externally and adjusting the pH to 4 with NaOH.

[0072] After detection, the leaching rate of bastnasite is 85.37%, the rare earth extraction rate is 97.38%, the rare earth back-extraction rate is 98.05%, and the recovery rate of aluminum ions is 98.4%.

[0073] Comparative Example 1

[0074] Carry out Comparative Example 1 according to Example 1. The differences between Comparative Example 1 and Example 1 include: The difference from Example 1 is that the rare earth concentrate is leached with 3 mol / L sulfuric acid.

[0075] Example 2

[0076] Carry out Example 2 according to Example 1. The differences between Example 2 and Example 1 include: The rare earth concentrate is leached with a mixed solution of 3 mol / L sulfuric acid and 0.15 mol / L aluminum sulfate.

[0077] Use 0.10 mol / L sodium hydroxide to absorb the overflowing fluoride ions in Comparative Example 1 and Example 2, and detect the fluoride ion content in the leachate every 15 minutes.

[0078] As Figure 3 shown, after the addition of aluminum salt, HF is complexed in the leachate and will not overflow into the air.

[0079] Example 3

[0080] Example 3 is carried out according to Example 1. The differences between Example 3 and Example 1 include: using a mixed solution of sulfuric acid and 0.3 mol / L aluminum sulfate to leach rare earth concentrate. Among them, the concentration of sulfuric acid can be set to 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, and 3.5 mol / L.

[0081] As Figure 4 shown, when the concentration of sulfuric acid is 1.5 - 3.5 mol / L, the rare earth leaching rate first increases and then decreases with the increase of sulfuric acid concentration.

[0082] Example 4

[0083] Example 4 is carried out according to Example 1. The differences between Example 4 and Example 1 include: the concentration of aluminum sulfate can be set to 0.15 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, and 0.5 mol / L.

[0084] As Figure 5 shown, when the concentration of aluminum sulfate is 0.15 - 0.50 mol / L, the rare earth leaching rate first increases and then decreases.

[0085] Example 5

[0086] Example 5 is carried out according to Example 1. The differences between Example 5 and Example 1 include: the liquid - solid ratio can be set to 26:1, 28:1, 30:1, 32:1, and 34:1.

[0087] As Figure 6 shown, when the liquid - solid ratio is 26 - 34:1, the rare earth leaching rate increases with the increase of the liquid - solid ratio. After the liquid - solid ratio is 32:1, the growth rate tends to be gentle. When the liquid - solid ratio is 40:1, it still has a good rare earth leaching rate.

[0088] Example 6

[0089] Example 6 is carried out according to Example 1. The differences between Example 6 and Example 1 include: the leaching reaction temperature can be set to 120 °C, 125 °C, 130 °C, 135 °C, and 140 °C.

[0090] As Figure 7 shown, when the leaching reaction temperature is 120 - 140 °C, the rare earth leaching rate increases with the increase of temperature. After the reaction temperature reaches 135 °C, the growth rate slows down.

[0091] Example 7

[0092] Example 7 is implemented according to Example 1. The differences between Example 7 and Example 1 include that the leaching reaction time can be set to 30 min, 60 min, 90 min, 120 min, and 150 min.

[0093] As Figure 8 shown, when the leaching reaction time is 0.5 - 2.5 h, the rare earth leaching rate increases with the extension of the reaction time. After the reaction time reaches 2.0 h, the growth rate slows down.

[0094] Example 8

[0095] Example 8 is implemented according to Example 1. The differences between Example 8 and Example 1 include: taking multiple groups of 20 ml of the second filtrate, adding ammonia water to the multiple groups of the second filtrate, and setting the pH values of the multiple groups of the second filtrate to -0.75, 1, 1.5, and 2 respectively; performing the first extraction treatment on the multiple groups of the second filtrate with triisooctylamine to obtain multiple groups of first raffinates; protonating the primary amine organic phase with 1 mol / L H2SO4, and performing the second extraction treatment on the multiple groups of the first raffinates with the protonated primary amine to obtain multiple groups of second raffinates containing fluorine and aluminum and multiple groups of second organic phases containing rare earths.

[0096] As Figure 9 shown, when the pH of the second filtrate is -0.75 - 2, with the increase of the initial pH of the second filtrate, the extraction rate of rare earth in the second organic phase increases. Increasing the initial pH value of the second filtrate is beneficial to rare earth extraction. However, the initial pH of the second filtrate cannot be increased continuously. The second filtrate contains a large amount of aluminum ions and rare earth ions. The maximum pH value can be adjusted to 2. If it is increased further, a large amount of precipitation will be generated, which is not conducive to extraction.

[0097] Example 9

[0098] Example 9 is implemented according to Example 1. The differences between Example 9 and Example 1 include: adding ammonia water to the second filtrate and setting the pH of the second filtrate to 2; performing extraction treatment on the first raffinate with protonated primary amine organic phases with different volumes, that is, performing extraction treatment on the first raffinate with protonated primary amine organic phases with different phase ratios.

[0099] As Figure 10 shown, with the increase of the phase ratio (i.e., the phase ratio), the extraction rate of rare earth in the second organic phase increases, and the extraction rate of aluminum ions in the first stage decreases. When the phase ratio is 3, the rare earth extraction rate reaches 94.83%. After that, increasing the phase ratio further has little effect. At this time, the extraction rate of aluminum ions is 6.09%.

[0100] Example 10

[0101] Example 10 was implemented according to Example 1. The differences between Example 10 and Example 1 include: treating the second filtrate by extraction with triisooctylamine at different phase ratios for the first time, and measuring the change in the concentration of useful ions in the first raffinate after treating the second filtrate with triisooctylamine at different phase ratios.

[0102] As Figure 11 shown, as the phase ratio of triisooctylamine increases, the concentrations of rare earth ions and aluminum ions in the first raffinate do not change, while the concentration of F - and the concentration of H + decrease continuously, and the pH value of the solution increases continuously, indicating that triisooctylamine can recover the excess acid in the solution without affecting rare earth ions and aluminum ions.

[0103] Example 11

[0104] Example 11 was implemented according to Example 1. The differences between Example 11 and Example 1 include: taking multiple groups of 20 ml of the second leaching solution with a pH value of 2; treating multiple groups of the second filtrate by extraction with triisooctylamine at different phase ratios for the first time; and then treating multiple groups of the first raffinate by extraction with unprotonated primary amine with a phase ratio of 3 for the second time, and measuring the first-stage extraction effect of unprotonated primary amine on extracting rare earth ions and aluminum ions after treating the second filtrate with triisooctylamine at different phase ratios.

[0105] As Figure 12 shown, as the phase ratio of triisooctylamine increases, the extraction rate of rare earth ions extracted by unprotonated primary amine with a phase ratio of 3 also increases. When the phase ratio of triisooctylamine is 2, the extraction rate of rare earth ions by primary amine in the first stage is 97.38%. Further increasing triisooctylamine has little effect on the extraction rate.

[0106] Example 12

[0107] Example 12 was implemented according to Example 1. The differences between Example 12 and Example 1 include: treating the second filtrate by extraction with triisooctylamine with a phase ratio of 2 for the first time; treating the first raffinate by extraction with unprotonated primary amine with a phase ratio of 3 for the second time to obtain a second raffinate and a second organic phase containing rare earths; and then backwashing the aluminum ions in the second organic phase containing rare earths with different concentrations of ammonium sulfate backwashing solution with a phase ratio of 1, and measuring the aluminum ion content and rare earth ion content in the backwashing solution after backwashing to determine the concentration range of ammonium sulfate solution.

[0108] As Figure 13 shown, after backwashing, the aluminum ion content in the backwashing solution increases with the increase of ammonium sulfate concentration. At the same time, the rare earth ion content in the backwashing solution also increases. When using ammonium sulfate solution with a mass percentage content of 3% as the backwashing solution, the aluminum ion content in the backwashing solution after backwashing is relatively high, and the rare earth ion content is very low.

[0109] Example 13

[0110] Example 13 is implemented according to Example 1. The differences between Example 13 and Example 1 include:

[0111] The second filtrate is subjected to a first extraction treatment with triisooctylamine with a phase ratio of 2; the first raffinate is subjected to a second extraction treatment with unprotonated primary amine with a phase ratio of 3; after the aluminum ions in the second organic phase containing rare earths are backwashed with an ammonium sulfate backwash solution with a phase ratio of 1, different chloride solutions (including hydrochloric acid, ammonium chloride, and magnesium chloride solutions) with a concentration of 2 mol / L are used for back-extraction, and the rare earth ions and aluminum ions in the back-extraction solution are measured to determine the back-extraction effect.

[0112] As Figure 14 shown, a single back-extraction with hydrochloric acid can achieve a back-extraction rate of 98.05%. The single back-extraction effects of ammonium chloride solution and magnesium chloride solution are not good, but through multi-stage back-extraction, the back-extraction rate can also reach more than 99.5%. Therefore, hydrochloric acid solution is preferably selected as the back-extraction liquid. When ammonium chloride and magnesium chloride solutions are used as the back-extraction liquid, multi-stage back-extraction (such as three-stage back-extraction) can be carried out to improve the back-extraction rate. And experiments show that increasing the concentration of hydrochloric acid results in better back-extraction effect. When back-extracting with 2 mol / L hydrochloric acid, c Al / c RE in the back-extraction liquid is 0.008, and the saturated rare earth concentration can reach 19.26 g / L.

[0113] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate, comprising the following steps: The rare earth ore is leached with a mixed solution containing sulfuric acid and aluminum sulfate, and then filtered to obtain a first filtrate; Calcium sulfate seeds are added to the first filtrate, and then filtered to obtain calcium sulfate crystals and a second filtrate; The second filtrate is subjected to a first extraction treatment to obtain a first raffinate and a first organic phase; The first organic phase is subjected to a first stripping treatment to obtain a mixed acid solution containing hydrofluoric acid and sulfuric acid; The first raffinate is subjected to a second extraction treatment to obtain a second raffinate and a second organic phase; The second organic phase is subjected to a second stripping treatment to obtain a mixed solution containing rare earth ions; and Sodium fluoride is added to the second raffinate, and a pH regulator is added to adjust the pH to 3-5, and then filtered to obtain cryolite.

2. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, In the mixed solution containing sulfuric acid and aluminum sulfate, the concentration range of sulfuric acid is 1.5-3.5 mol / L, and the concentration range of aluminum sulfate is 0.15-0.50 mol / L.

3. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, In the leaching treatment, the leaching temperature is 120-140 °C, the leaching time is 0.5-2.5 h, the stirring speed is 150-250 r / min, and the liquid-solid ratio is 10-40:

1.

4. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, At least one of the following conditions is satisfied: In the rare earth ore, the mineral particles are not less than 100 mesh; In the rare earth ore, the content of bastnasite is not less than 50%; The calcium sulfate seeds are calcium sulfate dihydrate and / or calcium sulfate; The addition amount of the calcium sulfate seeds is 0.05-0.5% of the mass of the first filtrate; The addition amount of sodium fluoride is 5-7 times the concentration of aluminum ions in the second raffinate; In the first stripping treatment, the stripping agent is water and / or the filtrate obtained by filtration during the preparation of cryolite; In the first extraction treatment, the extractant is triisooctylamine, the phase ratio is 0.5-4, the oscillation time is 5-30 min, and the extraction temperature is room temperature; In the second extraction treatment, the extractant is secondary carbon primary amine, the phase ratio is 0.5-4, the oscillation time is 5-30 min, and the extraction temperature is room temperature.

5. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, In the second stripping treatment, the concentration range of the stripping agent in the stripping solution is 1-6 mol / L, the stripping agent is at least one of hydrochloric acid, ammonium chloride and magnesium chloride, and the mixed solution containing rare earth ions contains rare earth chlorides.

6. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 5, characterized in that, Before the "second stripping treatment of the second organic phase", the method for recovering rare earth, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate further includes: The second organic phase is backwashed with a backwashing solution of 0.01-0.5 mol / L, wherein the backwashing solution includes a sulfuric acid solution and / or an ammonium sulfate solution, the phase ratio is 1-3, and the mixed solution containing rare earth ions contains rare earth sulfates and rare earth chlorides.

7. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, 5, or 6, characterized in that, The method for recovering rare earth, aluminum and fluorine by sulfuric acid leaching of rare earth ore assisted by aluminum sulfate further includes the following steps: At least one of sodium carbonate, sodium bicarbonate and ammonium bicarbonate is added to the mixed solution containing rare earth ions, and then filtered to obtain rare earth precipitate.

8. The method for recovering rare earths, aluminum and fluorine by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, The pH regulator is at least one of sodium carbonate, sodium bicarbonate and sodium hydroxide.

9. The method for recovering rare earths and aluminum fluoride by sulfuric acid leaching of rare earth ores assisted by aluminum sulfate according to claim 1, characterized in that, In the step of "adding sodium fluoride to the second raffinate and filtering to obtain cryolite", the reaction temperature is 20-100 °C and the reaction time is 20-70 min.

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