CN111961872A - Method for extracting valuable elements in calcium-thermal vacuum reduction rare earth slag - Google Patents
Method for extracting valuable elements in calcium-thermal vacuum reduction rare earth slag Download PDFInfo
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Abstract
The invention discloses a method for extracting valuable elements from calcium-thermal vacuum reduction rare-earth residues, which comprises the steps of uniformly mixing the calcium-thermal vacuum reduction rare-earth residues with lithium salt to obtain a mixture; and sequentially carrying out first-stage vacuum replacement and second-stage vacuum distillation on the obtained mixture to obtain the high-purity lithium fluoride. The invention adopts a vacuum replacement-vacuum distillation method to directly replace fluorine in the calcium thermal reduction rare earth slag with lithium salt to prepare lithium fluoride, and the distillation slag is subjected to leaching acid decomposition-extraction separation process to prepare rare earth fluoride or oxide, wherein the purity of the lithium fluoride is not lower than 99.9 percent, and the purity of the rare earth oxide is not lower than 99.5 percent, thereby realizing resource recovery of fluorine and rare earth elements in the calcium thermal reduction rare earth slag.
Description
Technical Field
The invention belongs to the technical field of rare earth residue resource recovery, and relates to a method for extracting valuable elements in calcium-thermal vacuum reduction rare earth residues, in particular to a method for extracting rare earth and fluorine in calcium-thermal vacuum reduction rare earth residues.
Background
The production of high melting point rare earth metal and low boiling point rare earth metal mainly adopts vacuum thermal reduction process. The low boiling point rare earth metals (such as Sm, Eu, Yb and Tm) are generally prepared by a vacuum lanthanum thermal reduction-distillation method, the generated slag consists of lanthanum oxide, a small amount of lanthanum metal, the prepared metal and oxides thereof, and the lanthanum oxide and the oxides of the prepared metal can be obtained by utilizing the existing separation process after the slag is dissolved in acid, so that the rare earth in the slag can be completely recovered. When producing high melting point rare earth metals (such as Gd, Tb, Dy, Ho, Er, Y, Lu metals, Tb-Dy alloys and the like), metallic calcium is generally adopted as a reducing agent, rare earth fluoride is adopted as a raw material, and the main component of the generated calcium thermal reduction slag is CaF2And 5-7% of rare earth (calculated as REO) remains.
The calcium thermal reduction slag is decomposed by using a leaching acid and extracted and separated process at presentLeaching and recovering rare earth accounting for 65.0 percent of the total amount of the rare earth in the reducing slag, wherein the residue still contains 2 to 3 percent of the rare earth, and the main reason is that the residue contains 34 percent of the rare earth in the slag and REF3Form exists, and REF3If the rare earth is to be recovered, other leaching agents are required to be selected, but most of calcium is dissolved out, even all of calcium is dissolved out, so that the recovery cost is greatly increased and is irretrievable; the leaching solution contains a large amount of calcium and high contents of iron, aluminum and silicon, and rare earth solution obtained after extraction and impurity removal can be used for preparing rare earth fluoride or rare earth oxide. Therefore, the recovery rate of the qualified rare earth prepared by recovering the rare earth from the calcium thermal reduction furnace slag is only 65.0 percent, and the fluorine in the slag is not comprehensively utilized. In order to further improve the comprehensive utilization rate of rare earth and fluorine, the development of an economic, simple-flow and environment-friendly 'green' metallurgical process is urgent.
Disclosure of Invention
Aiming at the defects of the existing technology for extracting valuable elements in the calcium-thermal vacuum reduction rare earth slag, the invention aims to provide a method for extracting valuable elements in the calcium-thermal vacuum reduction rare earth slag, which can effectively improve the recovery rate of the valuable elements and reduce the energy consumption and the production cost.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a method for extracting valuable elements from calcium-thermal vacuum reduction rare-earth residues comprises uniformly mixing calcium-thermal vacuum reduction rare-earth residues with lithium salt to obtain a mixture; and sequentially carrying out first-stage vacuum replacement and second-stage vacuum distillation on the obtained mixture to obtain the high-purity lithium fluoride.
The invention firstly adopts vacuum replacement to directly replace fluorine in the calcium thermal reduction rare earth slag by lithium salt to convert the fluorine into lithium fluoride, then vacuum distillation is carried out to evaporate the lithium fluoride to obtain high-purity lithium fluoride and residual distillation slag containing calcium oxide and rare earth oxide, and the distillation slag is further subjected to leaching acid decomposition-extraction separation process to prepare rare earth fluoride or oxide, thereby realizing resource recovery of fluorine and rare earth elements in the calcium thermal reduction rare earth slag, and the main process principle is as follows:
3Li2CO3+2REF3→6LiF+RE2O3+3CO2
Li2CO3+CaF2→2LiF+CaO+CO2
preferably, the addition amount of the lithium salt is 1.2-1.6 times of the theoretical calculated molar amount of fluorine in the calcium thermal vacuum reduction rare earth slag.
Preferably, the lithium salt is lithium carbonate.
Preferably, the mixture is firstly pressed, and the pressure is 5-10 Mpa.
Preferably, the conditions of the one-stage vacuum replacement are as follows: the temperature is 450-650 ℃, the vacuum degree is 10-15 Pa, and the time is 1-3 h.
Preferably, the conditions of the two-stage vacuum distillation are as follows: the temperature is 750-950 ℃, the vacuum degree is 30-40 Pa, and the time is 1-3 h.
Preferably, the distillation residue remained after the two-stage vacuum distillation is subjected to leaching acid decomposition, extraction separation, precipitation and firing processes in sequence to obtain the rare earth oxide.
Preferably, the distillation slag is subjected to counter-current leaching by adopting 3.0-6.0 mol/L HCl, leaching solution is extracted and separated by a P507-HCl system to obtain rare earth solution, and then the rare earth solution is precipitated by oxalic acid and then is calcined to prepare rare earth oxide.
The invention has the beneficial effects that:
(1) the invention adopts a vacuum replacement-vacuum distillation method to directly replace fluorine in the calcareous thermally reduced rare earth slag with lithium salt to prepare lithium fluoride, and the distilled slag is subjected to leaching acid decomposition-extraction separation process to prepare rare earth fluoride or oxide, wherein the purity of the lithium fluoride is not lower than 99.9 percent, and the purity of the rare earth oxide is not lower than 99.5 percent.
(2) The invention can obviously improve the yield of lithium, fluorine and rare earth, and the yield is not lower than 97.5 percent, 99.5 percent and 98.0 percent respectively.
(3) The raw materials of the invention contain high-value rare earth elements (such as Gd, Tb, Dy, Ho, Er, Lu metal, Tb-Dy alloy and the like), and the recovery rate of the rare earth elements can be improved from 65.00 percent to more than 98.00 percent by the invention.
(4) The inventionThe raw material contains solid waste CaF2The invention can prepare lithium fluoride with higher value than lithium carbonate, and fully utilize fluorine, thereby reducing pollution.
(5) The method has the advantages of low raw material cost, short process flow, simple equipment, strong operability, no secondary pollution and easy industrial scale production.
Drawings
FIG. 1 is a schematic process flow diagram of the present invention;
FIGS. 2 to 4 show the results of detection of the lithium fluoride product obtained in example 3;
FIG. 5 shows the measurement results of the gadolinium oxide product obtained in example 1;
FIG. 6 shows the results of detecting terbium oxide product obtained in example 2;
FIG. 7 shows the results of measuring dysprosium oxide products obtained in example 3;
fig. 8 is a result of measurement of the holmium oxide product obtained in example 4;
fig. 9 shows the results of the detection of the erbium oxide product obtained in example 5.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The present invention will be further described with reference to specific embodiments.
Example 1
Adding calcium thermal reduction gadolinium slag containing 6.51% of gadolinium, 48.51% of calcium and 44.91% of fluorine (calculated according to mass percentage) into a reactor, uniformly mixing the calcium thermal reduction gadolinium slag with lithium carbonate, wherein the addition amount of the lithium carbonate is 1.2 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting the mixture into a material pressing mold for pressing, and controlling the pressure during material pressing to be 6Mpa to obtain a cake-shaped material; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 10 Pa; electrifying, heating to 450 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 35Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.94%; and taking the gadolinium slag out of the tungsten crucible, leaching the gadolinium slag by using 5.0mol/L HCl in a counter current manner, carrying out Ca/Gd separation on the leaching solution by using a P507-HCl system to obtain a gadolinium chloride solution, and preparing gadolinium oxide by oxalic acid precipitation and ignition, wherein the purity of the gadolinium oxide is 99.99% by analysis. The yields of lithium, fluorine and gadolinium obtained were calculated to be 98.61%, 99.58% and 98.59%, respectively.
Example 2
Adding calcium thermal reduction terbium slag containing 6.13 percent of terbium, 47.85 percent of calcium and 46.03 percent of fluorine (calculated by mass percentage) into a reactor, uniformly mixing with lithium carbonate, wherein the addition amount of the lithium carbonate is 1.2 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure during material pressing is controlled at 6 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 10 Pa; electrifying, heating to 500 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 35Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.92%; then taking out the terbium slag in the tungsten crucible, carrying out countercurrent leaching by using 5.0mol/L HCl, carrying out Ca/Tb separation on leaching solution by using a P507-HCl system to obtain terbium chloride solution, and preparing terbium oxide by oxalic acid precipitation and ignition, wherein the purity of the terbium oxide is analyzed to be 99.99%. The yields of lithium, fluorine and terbium obtained by calculation were respectively 98.6%, 99.6% and 98.5%.
Example 3
Adding 5.82% of dysprosium, 48.68% of calcium and 45.41% of fluorine (by mass percent) calcium thermal reduction dysprosium slag and lithium salt into a reactor, uniformly mixing, wherein the addition amount of the lithium salt is 1.2 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure during material pressing is controlled at 6 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 10 Pa; electrifying, heating to 550 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 35Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; then taking the dysprosium slag out of the tungsten crucible, leaching the dysprosium slag by using 5.0mol/L HCl in a countercurrent way, carrying out Ca/Dy separation on the leaching solution by using a P507-HCl system to obtain a dysprosium chloride solution, and preparing dysprosium oxide by oxalic acid precipitation and ignition, wherein the purity of the dysprosium oxide is 99.6% by analysis. The yields of lithium, fluorine and dysprosium were calculated to be 98.56%, 99.59% and 98.64%, respectively.
Example 4
Adding 5.54% of holmium, 48.70% of calcium and 45.71% of fluorine (by mass percent) into a reactor, uniformly mixing the holmium through calcium thermal reduction and lithium salt, wherein the addition amount of the lithium salt is 1.2 times of the theoretical calculated molar amount of the fluorine content in the rare earth slag through calcium thermal vacuum reduction, putting the mixture into a material pressing mold, and pressing under the condition that the pressure is controlled at 6 MPa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 10 Pa; electrifying, heating to 600 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 35Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; and then taking out holmium slag in the tungsten crucible, carrying out countercurrent leaching by using 5.0mol/L HCl, carrying out Ca/Ho separation on leaching solution by using a P507-HCl system to obtain holmium chloride solution, and preparing holmium oxide by oxalic acid precipitation and ignition, wherein the analyzed purity of the holmium oxide is 99.9%. The calculated yields of lithium, fluorine and holmium are respectively 98.62%, 99.65% and 98.25%.
Example 5
Adding calcium thermal reduction erbium slag containing 6.25% of erbium, 47.96% of calcium and 45.60% of fluorine (calculated by mass percentage) into a reactor, uniformly mixing with lithium salt, wherein the addition amount of the lithium salt is 1.2 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure intensity during material pressing is controlled at 6 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 10 Pa; electrifying, heating to 650 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 35Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; and taking out erbium residues in the tungsten crucible, leaching the erbium residues in a countercurrent manner by using 5.0mol/L HCl, separating Ca/Er in leaching solution by using a P507-HCl system to obtain erbium chloride solution, and preparing erbium oxide by oxalic acid precipitation and ignition, wherein the purity of the erbium oxide is 99.99% by analysis. The calculated yields of lithium, fluorine and erbium were 98.62%, 99.65% and 98.25%, respectively.
Example 6
Adding calcium thermal reduction gadolinium slag containing 6.51% of gadolinium, 48.51% of calcium and 44.91% of fluorine (calculated by mass percentage) into a reactor, uniformly mixing with lithium salt, wherein the addition amount of the lithium salt is 1.4 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold for pressing, and controlling the pressure during material pressing to be 8 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 12 Pa; electrifying, heating to 450 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 40Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.94%; and taking the gadolinium slag out of the tungsten crucible, leaching the gadolinium slag by using 5.0mol/L HCl in a counter current manner, carrying out Ca/Gd separation on the leaching solution by using a P507-HCl system to obtain a gadolinium chloride solution, and preparing gadolinium oxide by oxalic acid precipitation and ignition, wherein the purity of the gadolinium oxide is 99.99% by analysis. The yields of lithium, fluorine and gadolinium obtained were calculated to be 97.65%, 99.62% and 98.61%, respectively.
Example 7
Adding calcium thermal reduction terbium slag containing 6.13 percent of terbium, 47.85 percent of calcium and 46.03 percent of fluorine (calculated by mass percentage) into a reactor, uniformly mixing with lithium salt, wherein the addition amount of the lithium salt is 1.4 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure during material pressing is controlled at 8 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 12 Pa; electrifying, heating to 500 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 40Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.92%; then taking out the terbium slag in the tungsten crucible, carrying out countercurrent leaching by using 5.0mol/L HCl, carrying out Ca/Tb separation on leaching solution by using a P507-HCl system to obtain terbium chloride solution, and preparing terbium oxide by oxalic acid precipitation and ignition, wherein the purity of the terbium oxide is analyzed to be 99.99%. The yields of lithium, fluorine and terbium were calculated to be 97.61%, 99.63% and 98.57%, respectively.
Example 8
Adding 5.82% of dysprosium, 48.68% of calcium and 45.41% of fluorine (by mass percent) calcium thermal reduction dysprosium slag and lithium salt into a reactor, uniformly mixing, wherein the addition amount of the lithium salt is 1.4 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure during material pressing is controlled at 8 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 12 Pa; electrifying, heating to 550 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 40Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; then taking the dysprosium slag out of the tungsten crucible, leaching the dysprosium slag by using 5.0mol/L HCl in a countercurrent way, carrying out Ca/Dy separation on the leaching solution by using a P507-HCl system to obtain a dysprosium chloride solution, and preparing dysprosium oxide by oxalic acid precipitation and ignition, wherein the purity of the dysprosium oxide is 99.6% by analysis. The yields of lithium, fluorine and dysprosium were calculated to be 97.57%, 99.67% and 98.51%, respectively.
Example 9
Adding 5.54% of holmium, 48.70% of calcium and 45.71% of fluorine (by mass percent) into a reactor, uniformly mixing the holmium through calcium thermal reduction and lithium salt, wherein the addition amount of the lithium salt is 1.4 times of the theoretical calculated molar amount of the fluorine content in the rare earth slag through calcium thermal vacuum reduction, putting the mixture into a material pressing mold, and pressing under the condition that the pressure is controlled at 8Mpa during material pressing; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 12 Pa; electrifying, heating to 600 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 40Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; and then taking out holmium slag in the tungsten crucible, carrying out countercurrent leaching by using 5.0mol/L HCl, carrying out Ca/Ho separation on leaching solution by using a P507-HCl system to obtain holmium chloride solution, and preparing holmium oxide by oxalic acid precipitation and ignition, wherein the analyzed purity of the holmium oxide is 99.9%. The calculated yields of lithium, fluorine and holmium are respectively 97.68%, 99.60% and 98.35%.
Example 10
Adding calcium thermal reduction erbium slag containing 6.25% of erbium, 47.96% of calcium and 45.60% of fluorine (calculated by mass percentage) into a reactor, uniformly mixing with lithium salt, wherein the addition amount of the lithium salt is 1.4 times of the theoretical calculated molar amount of the fluorine content in the calcium thermal vacuum reduction rare earth slag, putting into a material pressing mold, and pressing, wherein the pressure intensity during material pressing is controlled at 8 Mpa; putting the cake-shaped material into a tungsten crucible, then putting the tungsten crucible into a vacuum carbon tube furnace, vacuumizing the furnace, and controlling the vacuum degree to be 12 Pa; electrifying, heating to 650 ℃, controlling the vacuum degree to 15Pa, and keeping the temperature for 2 h; then heating to 800 ℃, controlling the vacuum degree to 40Pa, and keeping the temperature for 2 h; and after cooling for 2 hours, closing the large vacuum butterfly valve and the power supply of the vacuum gauge, closing other vacuum butterfly valves, finally filling Ar to-0.06 Mpa, cooling for 4 hours, and discharging. After the system is cooled in air, taking out a product in a nickel-grade Hardgrove collector, and analyzing that the purity of lithium fluoride is 99.95%; and taking out erbium residues in the tungsten crucible, leaching the erbium residues in a countercurrent manner by using 5.0mol/L HCl, separating Ca/Er in leaching solution by using a P507-HCl system to obtain erbium chloride solution, and preparing erbium oxide by oxalic acid precipitation and ignition, wherein the purity of the erbium oxide is 99.99% by analysis. The calculated yields of lithium, fluorine and erbium were 97.68%, 99.75% and 98.45%, respectively.
Claims (8)
1. A method for extracting valuable elements in calcium-thermal vacuum reduction rare earth slag is characterized by comprising the following steps: uniformly mixing the calcium-thermal vacuum reduction rare earth slag and the lithium salt to obtain a mixture; and sequentially carrying out first-stage vacuum replacement and second-stage vacuum distillation on the obtained mixture to obtain the high-purity lithium fluoride.
2. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 1, wherein the method comprises the following steps: the addition amount of the lithium salt is 1.2-1.6 times of the theoretical calculated molar amount of fluorine in the thermal vacuum reduction rare earth slag of calcium.
3. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 2, wherein the method comprises the following steps: the lithium salt is lithium carbonate.
4. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 1, wherein the method comprises the following steps: the mixture is pressed at first, and the pressure is 5-10 MPa.
5. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 1, wherein the method comprises the following steps: the conditions of the first-stage vacuum replacement are as follows: the temperature is 450-650 ℃, the vacuum degree is 10-15 Pa, and the time is 1-3 h.
6. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 1, wherein the method comprises the following steps: the conditions of the two-stage vacuum distillation are as follows: the temperature is 750-950 ℃, the vacuum degree is 30-40 Pa, and the time is 1-3 h.
7. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth residues as claimed in any one of claims 1 to 6, wherein the method comprises the following steps: and (3) after the two-stage vacuum distillation, the distillation residues are remained, and the rare earth oxide is obtained by sequentially carrying out leaching acid decomposition, extraction separation, precipitation and firing processes.
8. The method for extracting valuable elements from the hot calcium vacuum reduction rare earth slag according to claim 7, wherein the method comprises the following steps: the distillation residues are subjected to counter-current leaching by adopting 3.0-6.0 mol/L HCl, leaching solution is subjected to extraction separation by a P507-HCl system to obtain rare earth solution, and then the rare earth solution is subjected to oxalic acid precipitation and then is burned to prepare rare earth oxide.
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| CN116497241B (en) * | 2023-07-03 | 2023-09-19 | 赣州晨光稀土新材料有限公司 | Method for recovering terbium element in terbium calcium slag |
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