Method for ammonium-free enrichment of rare earth mother liquor

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a method for ammonium-free enrichment of rare earth mother liquor. The preparation method comprises the following steps: mixing magnesium oxide and water, and carrying out ultrasonic stirring or ultra-long-time stirring to obtain magnesium oxide slurry; the magnesium oxide is analytically pure magnesium oxide, magnesium oxide with industrial purity of 85%, magnesium oxide with industrial purity of 95.4% or magnesium oxide with industrial purity of 90%; mixing the magnesium oxide slurry with the rare earth leaching mother liquor, and carrying out precipitation reaction under a stirring condition to obtain mixed slurry; and carrying out solid-liquid separation on the mixed slurry to obtain the rare earth enrichment. According to the method, the magnesium oxide crystals can be effectively crushed and dispersed through ultrasonic stirring and ultra-long-time stirring, so that more active sites are exposed on the surfaces of the magnesium oxide crystals, the activity and the reaction speed of magnesium oxide are favorably improved, the rare earth recovery rate is improved, and the purity of a rare earth product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for ammonium-free enrichment of rare earth mother liquor. Background Art

[0002] Ionic rare earth ore, also known as ion adsorption rare earth ore or weathering crust leaching rare earth ore, is a rare mineral resource in the world, rich in medium and heavy rare earths. For many years, ionic rare earth ore has been mined using an in-situ leaching process with ammonium sulfate as a leaching agent and ammonium bicarbonate as a precipitant, resulting in ammonia nitrogen pollution.

[0003] Researchers have conducted a detailed study on the composition of ionic rare earth mines and found that ionic rare earth mines are magnesium deficient. They innovatively used magnesium sulfate as a leaching agent and invented the magnesium sulfate leaching-magnesium oxide enrichment process, which solved the problem of excessive ammonia nitrogen in wastewater and was conducive to the clean production of the rare earth industry. In view of the low concentration of the comprehensive mother liquor in ionic rare earth mines, magnesium oxide is used for one-time precipitation enrichment, which reduces the impurity removal link of the traditional process, reduces the loss of rare earths, and improves the recovery rate of rare earths. However, due to the characteristics of magnesium oxide being slightly soluble in water, the rare earth product content is not high, but the impurity content is high. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for ammonium-free enrichment of rare earth mother liquor, which can improve the rare earth recovery rate, reduce the consumption of magnesium oxide, reduce the impurity content in the rare earth product, and improve the purity of the rare earth product.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for ammonium-free enrichment of rare earth mother liquor, comprising the following steps:

[0007] Mixing magnesium oxide and water, and performing ultrasonic stirring or ultra-long stirring to obtain magnesium oxide slurry;

[0008] The magnesium oxide is analytical pure magnesium oxide, industrial purity 85% magnesium oxide, industrial purity 95.4% magnesium oxide or industrial purity 90% magnesium oxide;

[0009] The ultra-long stirring time is ≥48h;

[0010] When the magnesium oxide is analytically pure magnesium oxide, the ultra-long stirring time is ≥ 2h;

[0011] The magnesium oxide slurry and the rare earth leaching mother solution are mixed and subjected to precipitation reaction under stirring conditions to obtain a mixed slurry;

[0012] The mixed slurry is separated into solid and liquid to obtain a rare earth enriched product.

[0013] Preferably, the particle size of the magnesium oxide is 200-250 mesh.

[0014] Preferably, the activity of the magnesium oxide is 65-80%.

[0015] Preferably, the mass ratio of the magnesium oxide to the rare earth in the rare earth leaching mother solution is 1.2 to 2.1:1.

[0016] Preferably, the concentration of magnesium oxide in the magnesium oxide slurry is 5 to 20 g / L.

[0017] Preferably, the ultrasonic power of the ultrasonic stirring is 80 to 100 Hz; and the time of the ultrasonic stirring is 2 to 3 hours.

[0018] Preferably, the rotation speed of the ultra-long time stirring is 600-800 rpm.

[0019] Preferably, the mass concentration of rare earth in the rare earth leaching mother solution is 0.24-0.44 g / L.

[0020] Preferably, the stirring speed is 600-800 rpm; and the stirring time is 1-3 h.

[0021] Preferably, after the solid-liquid separation, the method further comprises: drying the solid obtained by the solid-liquid separation to obtain a rare earth enriched product; the drying temperature is 100 to 110° C.; and the drying time is 7 to 10 hours.

[0022] The present invention provides a method for ammonium-free enrichment of rare earth mother liquor, comprising the following steps: mixing magnesium oxide and water, performing ultrasonic stirring or ultra-long stirring to obtain magnesium oxide slurry; the magnesium oxide is analytical pure magnesium oxide, industrial purity 85% magnesium oxide, industrial purity 95.4% magnesium oxide or industrial purity 90% magnesium oxide; the ultra-long stirring time is ≥48h; when the magnesium oxide is analytical pure magnesium oxide, the ultra-long stirring time is ≥2h; the magnesium oxide slurry is mixed with rare earth leaching mother liquor, and precipitation reaction is performed under stirring conditions to obtain a mixed slurry; the mixed slurry is solid-liquid separated to obtain a rare earth enrichment. The present invention can effectively break and disperse magnesium oxide crystals through ultrasonic stirring and ultra-long stirring, so that more active sites are exposed on the surface, which is helpful to improve the activity and reaction speed of magnesium oxide, improve the dispersibility and stability of magnesium oxide slurry, thereby improving the rare earth recovery rate, reducing the consumption of magnesium oxide, reducing the impurity (magnesium ion) content in rare earth products, and improving the purity of rare earth products. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic flow diagram of the method for ammonium-free enrichment of rare earth mother liquor in the present invention;

[0024] Figure 2This is a schematic flow diagram of the method for ammonium-free enrichment of rare earth mother liquor in Examples 8 to 9 of the present invention;

[0025] Figure 3 The SEM images of magnesium oxide with different purity and activity;

[0026] Figure 4 The SEM images of magnesium oxide with different purity and activity;

[0027] Figure 5 This is a graph showing the effect of the amount of industrial purity 90% magnesium oxide added on the rare earth concentration of the supernatant after precipitation;

[0028] Figure 6 This is a graph showing the effect of the addition amount of 90% industrial purity magnesium oxide on rare earth enrichment;

[0029] Figure 7 This is a graph showing the effect of the amount of added 90% ultrasonically pure magnesium oxide on the rare earth concentration in the supernatant after precipitation;

[0030] Figure 8 This is a graph showing the effect of the addition of 90% ultrasonic industrial purity magnesium oxide on rare earth enrichment;

[0031] Fig. 9 is the SEM image of untreated magnesium oxide;

[0032] Fig.10 is the SEM image of magnesium oxide after ultrasound;

[0033] Fig.11 This is the SEM image of magnesium oxide after extremely long stirring. DETAILED DESCRIPTION

[0034] The present invention provides a method for ammonium-free enrichment of rare earth mother liquor, comprising the following steps:

[0035] Mixing magnesium oxide and water, and performing ultrasonic stirring or ultra-long stirring to obtain magnesium oxide slurry;

[0036] The magnesium oxide is analytical pure magnesium oxide, industrial purity 85% magnesium oxide, industrial purity 95.4% magnesium oxide or industrial purity 90% magnesium oxide;

[0037] The ultra-long stirring time is ≥48h;

[0038] When the magnesium oxide is analytically pure magnesium oxide, the ultra-long stirring time is ≥ 2h;

[0039] The magnesium oxide slurry and the rare earth leaching mother solution are mixed and subjected to precipitation reaction under stirring conditions to obtain a mixed slurry;

[0040] The mixed slurry is separated into solid and liquid to obtain a rare earth enriched product.

[0041] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.

[0042] The invention mixes magnesium oxide and water, and performs ultrasonic stirring or ultra-long time stirring to obtain magnesium oxide slurry.

[0043] In the present invention, the particle size of the magnesium oxide is preferably 200-250 mesh, more preferably 220 mesh; the activity of the magnesium oxide is preferably 65-80%, more preferably 67%, 76.4%, 76.94% or 80%.

[0044] In the present invention, the magnesium oxide is analytically pure magnesium oxide, industrially pure 85% magnesium oxide, industrially pure 95.4% magnesium oxide or industrially pure 90% magnesium oxide, preferably industrially pure 90% magnesium oxide; the activity of the industrially pure 85% magnesium oxide is preferably 76.94% or 76.4%; the activity of the industrially pure 95.4% magnesium oxide is preferably 80%; the activity of the industrially pure 90% magnesium oxide is preferably 67%.

[0045] The purity of magnesium oxide not only affects its activity and reaction efficiency, but also may affect its compatibility and stability with other substances. High-purity magnesium oxide contains fewer impurities, which helps to improve its activity and reaction efficiency. However, the activity of magnesium oxide also affects the precipitation effect, so the present invention balances the purity and activity of magnesium oxide to effectively improve the product quality of rare earth enriched products.

[0046] In the present invention, the concentration of magnesium oxide in the magnesium oxide slurry is preferably 5 to 20 g / L, more preferably 10 g / L.

[0047] In the present invention, the ultrasonic power of the ultrasonic stirring is preferably 80-100 Hz, more preferably 90 Hz; the time of the ultrasonic stirring is preferably 2-3 h, more preferably 2 h; the stirring rate of the ultrasonic stirring is preferably 600-800 rpm, more preferably 700 rpm; the ultrasonic stirring is preferably carried out at room temperature.

[0048] In the present invention, the rotation speed of the ultra-long time stirring is preferably 600-800 rpm, more preferably 700 rpm; the time of the ultra-long time stirring is ≥48h, preferably 48h; the ultra-long time stirring is preferably carried out at room temperature.

[0049] When the magnesium oxide is analytically pure magnesium oxide, the ultra-long stirring time is ≥ 2 h, preferably 2 h; and the ultra-long stirring is preferably carried out at room temperature.

[0050] Magnesium oxide hydrolysis reaction: Magnesium oxide is a weakly alkaline oxide. It will undergo hydrolysis reaction when it meets water to produce magnesium hydroxide. The reaction formula is as follows: MgO+H 2 O→Mg(OH) 2 .

[0051] In the present invention, ultrasonic treatment generates high-frequency compression and rarefaction waves in liquid, forms tiny eddies and shear forces, helps to break weak bonds between crystals, and promotes the formation and growth of crystals. In addition, ultrasound can also increase the contact area between water and magnesium oxide, provides more nucleation points, and helps to form smaller and more uniform crystals. Super long time stirring treatment can also improve the morphology of magnesium oxide crystals. Therefore, ultrasound and super long time stirring can effectively break and disperse magnesium oxide crystals, expose more active sites on their surfaces, and help to improve the activity and reaction speed of magnesium oxide. The influence of ultrasonic treatment on the morphology of magnesium oxide crystals is significantly better than super long time stirring treatment.

[0052] After obtaining the magnesium oxide slurry, the present invention mixes the magnesium oxide slurry with rare earth leaching mother liquor, performs precipitation reaction under stirring conditions, and obtains a mixed slurry.

[0053] In the present invention, the mass concentration of rare earth in the rare earth leaching mother solution is preferably 0.24-0.44 g / L, more preferably 0.44 g / L.

[0054] In the present invention, the main components and distribution of the rare earth leaching mother solution are shown in Tables 1 to 6.

[0055] Table 1 Main components of rare earth leaching mother liquor raw material 1#

[0056] project REO Mg Fe Al Si Result (g / L) 0.24 1.10 0.00026 0.00079 0.016

[0057] Table 2 Rare earth leaching mother liquor raw material 1# rare earth distribution

[0058]

[0059] Table 3 Main components of rare earth leaching mother liquor raw material 2#

[0060] project REO Mg Fe Al Si Result (g / L) 0.44 1.56 0.00032 0.14 0.020

[0061] Table 4 Rare earth leaching mother liquor raw material 2# rare earth distribution

[0062]

[0063] Table 5 Main components of rare earth leaching mother liquor raw material 3#

[0064] project REO Mg Fe Al Si Result (g / L) 0.42 0.98 0.00022 0.00082 0.013

[0065] Table 6 Rare earth leaching mother liquor raw material 3# rare earth distribution

[0066]

[0067] In the present invention, the mass ratio of the magnesium oxide to the rare earth in the rare earth leaching mother solution is preferably 1.2 to 2.1:1, and more preferably 1.7 to 2.0:1.

[0068] In the present invention, the stirring speed is preferably 600-800 rpm, more preferably 700 rpm; the stirring time is preferably 1-3 h, more preferably 1 h; and the stirring is preferably performed at room temperature.

[0069] Reaction of magnesium oxide slurry and rare earth: Rare earth leaching mother liquor reacts with slurried magnesium oxide. As the pH value of the solution increases, rare earth ions combine with magnesium ions and hydroxide ions to form insoluble rare earth hydroxide precipitates. The precipitation reaction formula is as follows:

[0070] 3MgO+2RE 3+ +3H 2 O→2RE(OH) 3 ↓+3Mg 2+ .

[0071] After obtaining the mixed slurry, the present invention separates the mixed slurry into solid and liquid to obtain a rare earth enriched product.

[0072] In the present invention, the solid-liquid separation is preferably filtration; the filtration is preferably suction filtration. The present invention has no special limitation on the filtration process, and any filtration process known in the art can be used.

[0073] After the solid-liquid separation, the present invention preferably further comprises: drying the solid obtained by the solid-liquid separation to obtain a rare earth enriched product.

[0074] In the present invention, the drying temperature is preferably 100-110° C., more preferably 105° C.; the drying time is preferably 7-10 h, more preferably 8 h.

[0075] In the present invention, the filtrate obtained by the solid-liquid separation is preferably used as the supernatant.

[0076] The present invention dries the rare earth enriched material to prevent the rare earth enriched material from fluidizing during the treatment and transportation process due to a high water content, thereby affecting its uniformity and stability, and thus affecting the quality of the product and the treatment efficiency.

[0077] Figure 1 The schematic diagram of the process for ammonium-free enrichment of rare earth mother liquor in the present invention is as follows: Figure 1 It can be seen that the present invention mixes magnesium oxide and water and stirs them to make magnesium oxide slurry, and then adds leaching mother liquor and stirs them to enrich rare earth and obtain rare earth products.

[0078] Figure 2 The schematic diagram of the process for ammonium-free enrichment of rare earth mother liquor in Examples 8 to 9 of the present invention is as follows: Figure 2 It can be seen that the magnesium oxide is slurried by ultrasonicating the magnesium oxide and water for 2 hours, or stirring the magnesium oxide and water for 48 hours.

[0079] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0080] Example 1 (using analytically pure magnesium oxide as raw material)

[0081] Analytically pure magnesium oxide powder (particle size 220 mesh) was mixed with water and stirred at 700 rpm for 2 h at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L;

[0082] The magnesium oxide slurry was slowly added to the rare earth leaching mother liquor (0.24 g / L, raw material 1#), and stirred at 700 rpm for 1 hour at room temperature, wherein the mass of magnesium oxide was 1.4 times the mass of rare earth in the rare earth leaching mother liquor, to achieve rare earth enrichment, and the obtained mixed slurry was filtered to obtain a solid and a filtrate, respectively, and the obtained solid was dried at 105° C. for 8 hours to obtain a rare earth enriched product, and the filtrate was collected at the same time.

[0083] Example 2 (using industrial purity 90% magnesium oxide (currently used in mines) as raw material)

[0084] Industrial purity 90% magnesium oxide powder (activity 67%, particle size 220 mesh) was mixed with water and ultrasonically stirred at 90 Hz and 700 rpm for 2 h at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L;

[0085] The magnesium oxide slurry was slowly added to the rare earth leaching mother liquor (0.44 g / L, raw material 2#), and stirred at 700 rpm for 1 hour at room temperature, wherein the mass of magnesium oxide was 1.7 times the mass of rare earth in the rare earth leaching mother liquor, to achieve rare earth enrichment, and the obtained mixed slurry was filtered to obtain a solid and a filtrate, respectively, and the obtained solid was dried at 105° C. for 8 hours to obtain a rare earth enriched product, and the filtrate was collected at the same time.

[0086] Example 3 (using industrial purity 90% magnesium oxide (currently used in mines) as raw material)

[0087] The difference from Example 2 is that industrial 90% magnesium oxide powder is mixed with water and stirred at 700 rpm for 48 hours at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L, and the mass of magnesium oxide is 2.1 times the mass of rare earth in the rare earth leaching mother liquor.

[0088] Example 4 (using industrial purity 90% magnesium oxide (currently used in mines) as raw material)

[0089] The difference from Example 2 is that industrial 90% magnesium oxide powder is mixed with water and stirred at 700 rpm for 48 hours at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L, and the mass of magnesium oxide is 1.8 times the mass of rare earth in the rare earth leaching mother liquor.

[0090] Example 5 (using industrial purity 90% magnesium oxide (currently used in mines) as raw material)

[0091] The difference from Example 2 is that industrial 90% magnesium oxide powder is mixed with water and ultrasonically stirred at 90 Hz and 700 rpm for 2 h at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L, and the mass of magnesium oxide is 1.8 times the mass of rare earth in the rare earth leaching mother liquor.

[0092] Example 6 (using industrial purity 85% magnesium oxide (76.94% activity) as raw material)

[0093] The difference from Example 2 is that the industrial purity 90% magnesium oxide is replaced by industrial purity 85% magnesium oxide (76.94% activity, particle size of 220 mesh), and the mass of magnesium oxide is 1.8 times the mass of rare earth in the rare earth leaching mother liquor.

[0094] Example 7 (using industrial 95.4% magnesium oxide (80% activity) as raw material)

[0095] The difference from Example 2 is that the industrial purity 90% magnesium oxide is replaced by industrial purity 95.4% magnesium oxide and the mass of the magnesium oxide is 1.7 times the mass of the rare earth in the rare earth leaching mother liquor.

[0096] Example 8

[0097] Mix industrial grade 90% pure magnesium oxide (activity of 67%, particle size of 220 mesh) and water, and stir ultrasonically at 90 Hz and 700 rpm for 2 h at room temperature to obtain a magnesium oxide slurry with a concentration of 10 g / L;

[0098] The magnesium oxide slurry was added to the rare earth leaching mother liquor (0.24 g / L, raw material 1#) by a peristaltic pump, and stirred at 700 rpm for 3 hours at room temperature, wherein the mass of magnesium oxide was 1.8 times the mass of rare earth in the rare earth leaching mother liquor, to achieve rare earth enrichment, and the obtained mixed slurry was filtered to obtain a solid and a filtrate, respectively, and the obtained solid was dried at 105° C. for 8 hours to obtain a rare earth enriched product, and the filtrate was collected at the same time.

[0099] Example 9

[0100] The difference from Example 8 is that industrial grade 90% pure magnesium oxide and water are mixed and stirred at 700 rpm for 48 hours to obtain a magnesium oxide slurry with a concentration of 10 g / L.

[0101] Performance Testing

[0102] (1) Structural characterization and reaction mechanism analysis of magnesium oxide

[0103] In the in-depth study of the slurry preparation process and reaction activity of magnesium oxide, scanning electron microscopy (SEM) technology was used to characterize the surface morphology, crystal morphology, texture and void mechanism of magnesium oxide. Through SEM analysis, the microstructure and surface characteristics of magnesium oxide are revealed, providing important visual evidence for understanding its behavior during slurry preparation and reaction processes. The results are shown in Figures 3-4 A is the SEM characterization of analytical pure magnesium oxide, B is the SEM characterization of magnesium oxide with a purity of 90% and an activity of 67% for mining, C is the SEM characterization of magnesium oxide with a purity of 95.4% and an activity of 80%, D is the SEM characterization of magnesium oxide with a purity of 96%, and E is the SEM characterization of magnesium oxide with a purity of 85% and an activity of 76.4%.

[0104] Depend on Figure 3 and Figure 4 SEM image analysis shows that the superior performance of analytically pure magnesium oxide in the slurry process is mainly attributed to its lower surface energy, smaller grain size and fewer surface defects. These characteristics make magnesium oxide more stable during the slurry process and avoid aggregation, thus achieving excellent slurry effect. In contrast, magnesium oxide with higher activity provides more active sites due to its larger specific surface area, more surface defects and stronger surface adsorption capacity, which helps to improve its activity during the reaction. Although magnesium oxide with high activity may face certain challenges during the slurry process, its reaction effect is still satisfactory. However, high-purity magnesium oxide may have certain limitations in terms of reaction activity. High purity means that the impurity content in magnesium oxide is lower, which may limit the number and type of surface active sites, thereby affecting its reaction activity. In addition, the crystal structure of high-purity magnesium oxide may be more complete and ordered, resulting in lower surface energy, which is not conducive to the adsorption and reaction of reactant molecules. Therefore, when selecting magnesium oxide as a reactant, it is necessary to balance purity and activity to achieve the best reaction performance.

[0105] Through SEM analysis, it was found that analytically pure magnesium oxide performed best in the slurry adjustment process due to its lower surface energy, smaller grains and fewer surface defects. Magnesium oxide with high activity provides more active sites during the reaction due to its larger specific surface area, more surface defects and stronger surface adsorption capacity, thereby improving its reactivity. However, high-purity magnesium oxide may have certain limitations in terms of reactivity, and a trade-off needs to be made between purity and activity.

[0106] (2) Test of industrial purity 90% magnesium oxide (currently used in mines, activity 67%)

[0107] 1) Test under normal temperature conditions

[0108] This experiment explored the effect of the dosage of industrial purity 90% magnesium oxide on the precipitation effect of rare earth leaching solution. The experiment used 0.24g / L mine leaching mother liquor as raw material, and added different multiples (1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times, 2.5 times) of industrial 90% magnesium oxide as a precipitant. Figure 5 and Figure 6 The changes of rare earth content and magnesium ion content in the precipitate (dried but not calcined) with the amount of magnesium oxide used are shown respectively.

[0109] from Figure 5 It can be seen that the greater the amount of magnesium oxide used, the more complete the precipitation of rare earths in the mother liquor. However, due to the large amount of impurities and uncontrollable factors in industrial magnesium oxide, the precipitation effect fluctuates. When the amount of magnesium oxide is 2.3 times, the precipitation effect is better.

[0110] from Figure 6 It can be seen that the rare earth content in the precipitate first increases and then decreases with the increase in the amount of magnesium oxide. When the amount of magnesium oxide is between 2.3 and 2.5 times, the rare earth content in the precipitate reaches the highest value, and the product quality is relatively close. The observation results show that under normal temperature conditions, the performance of 90% pure magnesium oxide used in the laboratory failed to achieve the expected effect.

[0111] 2) Ultrasonic condition test

[0112] Because the results obtained with industrial purity 90% magnesium oxide at room temperature are not ideal, in order to obtain an ideal enrichment, this experiment studies the effect of the amount of 90% pure magnesium oxide on the precipitation effect of rare earth leaching solution under ultrasonic conditions. This experiment uses 0.44g / L mine leaching mother liquor as raw material, stirs it for 2h under ultrasonic conditions, and adds different multiples (1.4 times, 1.7 times, 2.0 times) of 10g / L concentration of 90% magnesium oxide slurry as a precipitant. Figure 7 and Figure 8The changing trends of rare earth content and magnesium ion content in the precipitate (dried but not calcined) with the amount of magnesium oxide used are shown respectively.

[0113] Depend on Figure 7 and Figure 8 It can be seen that in this experiment, the effect of different proportions of 90% pure magnesium oxide on the precipitation effect of rare earth leachate was investigated by stirring under ultrasonic conditions. The test results show that there is a positive correlation between the increase in the amount of magnesium oxide and the rare earth precipitation efficiency. Specifically, when the amount of magnesium oxide is 2.0 times, the precipitation effect is optimal, and the rare earth content in the supernatant is the lowest, indicating that the appropriate amount of magnesium oxide can effectively promote the precipitation of rare earth ions. Further analysis shows that when 1.4 times 90% magnesium oxide slurry is used, the rare earth content in the enriched material after precipitation is the highest, which is equivalent to the amount of analytical pure magnesium oxide. However, the rare earth content in the supernatant is high, which may be due to the insufficient amount of magnesium oxide, which failed to completely precipitate the rare earth ions in the solution. Taking all factors into consideration, the amount of 90% magnesium oxide of about 1.7 times seems to be a more reasonable choice, because it can effectively precipitate rare earths while controlling the increase in the rare earth content in the supernatant to achieve a balanced precipitation effect.

[0114] In summary, the test results show that ultrasound has a significant improvement on magnesium oxide slurry. It is recommended to use about 1.7 times the purity of 90% magnesium oxide slurry as a precipitant in practical applications to achieve the best rare earth enrichment effect.

[0115] 3) Ultra-long stirring test

[0116] This experiment aims to explore the effect of ultra-long stirring time on the uniformity of magnesium oxide slurry. By controlling the stirring time to achieve a more uniform mixing of the slurry, 2.1 times the conventional amount of 90% magnesium oxide was used in the experiment. Table 7 shows the specific results of the test after drying the product.

[0117] Table 7 Effect of adding 90% industrial purity magnesium oxide on rare earth enrichment during long-term stirring

[0118]

[0119] The test results show that extending the stirring time has a significant effect on increasing the content of rare earth elements (REO) in rare earth concentrates. This may be because extending the stirring time helps to disperse and mix the magnesium oxide more fully, thereby promoting the chemical reaction between the rare earth elements and magnesium oxide. In addition, longer stirring may help to improve the homogenization of the slurry, increase the contact area between magnesium oxide and rare earth minerals, and thus improve the extraction efficiency of rare earth elements. Overall, extending the stirring time is an effective method for optimizing the rare earth extraction process and increasing the rare earth content in the product.

[0120] 4) SEM comparison of the effects of ultrasound and stirring on the morphology of magnesium oxide

[0121] In order to find out more thoroughly why the magnesium oxide slurry has better conditions, the following SEM electron microscope analysis was performed on the 90% pure magnesium oxide after ultrasound. The results are as follows: Figures 9-11 As shown, Fig. 9 For untreated magnesium oxide, Fig.10 is magnesium oxide after ultrasound, Fig.11 It is magnesium oxide after being stirred for a very long time.

[0122] Through electron microscopy, it can be seen that ultrasound and ultra-long stirring of 90% magnesium oxide can effectively break and disperse magnesium oxide crystals, exposing more active sites on its surface. This helps to improve the activity and reaction rate of magnesium oxide.

[0123] But at the same time, the effect of ultrasonic treatment on the morphology of magnesium oxide crystals is significantly better than that of ultra-long stirring treatment. Ultrasonic treatment produces high-frequency compression and rarefaction waves in the liquid, forming tiny eddies and shear forces, which help break the weak bonds between crystals and promote the formation and growth of crystals. In addition, ultrasound can also increase the contact area between the solution and magnesium oxide, provide more nucleation points, and help form smaller and more uniform crystals. In contrast, although ultra-long stirring treatment can provide a more uniform nucleation environment and promote material diffusion, the shear force and eddies generated are not enough to compete with ultrasonic treatment, so its effect is relatively weak. However, ultra-long stirring treatment still has a certain positive effect and can improve the morphology of magnesium oxide crystals.

[0124] In summary, ultrasonic treatment may be more conducive to the formation of fine and uniform magnesium oxide crystals due to its unique mechanical and physical effects. Ultra-long stirring also has a certain positive effect, but its effect may not be as significant as ultrasonic treatment.

[0125] 5) Expanded test of ultrasonic and long-term stirring stability of industrial purity 90% magnesium oxide

[0126] According to the results obtained under the above test conditions, ultrasonic treatment and ultra-long stirring showed significant results. Therefore, this treatment method will be subjected to a stability expansion test to further verify its effect. The test used 10 times the base amount of 90% pure magnesium oxide, and the stability expansion test was carried out at 1.7 times and 1.8 times the dosage respectively. The test process includes ultrasonic treatment (frequency 90Hz, time 2h) and ultra-long stirring (time 48h), followed by drying and burning tests of the samples. The following is a professional description of the test results after drying the product, and the results are shown in Table 8:

[0127] Table 8 Results of ultrasonic and long-time stirring stability expansion test of industrial purity 90% magnesium oxide

[0128]

[0129] The test results show that under ultrasonic treatment conditions, the test group with 1.8 times the amount of magnesium oxide added showed a better rare earth precipitation effect, and the rare earth content of the supernatant after precipitation was only 0.24 mg / L, significantly lower than the 30.32 mg / L of the group with 1.7 times the amount of magnesium oxide added. This shows that 1.8 times the amount of magnesium oxide added has a clear advantage in improving the purity of rare earth separation.

[0130] In terms of the burning content of rare earth enriched products, the REO content of the group with 1.8 times the amount of magnesium oxide added was 39.94%, slightly higher than the 39.12% of the group with 1.7 times. This shows that under the 1.8 times condition, the enrichment effect of rare earth is slightly better. In addition, the burning loss rate of the group with 1.8 times the amount of magnesium oxide added was 29.38%, which was higher than the 23.46% of the group with 1.7 times. This may indicate that under the 1.8 times condition, more impurities were removed during the burning process, thereby improving the purity of the rare earth enriched products.

[0131] Based on the above test data analysis, it can be concluded that under ultrasonic treatment conditions, 1.8 times the amount of magnesium oxide added shows superior performance in improving the precipitation effect of rare earth elements, the purity of rare earth enriched products and the effective utilization of magnesium compared with 1.7 times the amount added. Therefore, from the test results, 1.8 times the amount of magnesium oxide added can be regarded as the best choice under ultrasonic treatment conditions, with good stability and repeatability.

[0132] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for ammonium-free enrichment of rare earth mother liquor, characterized in that: The following steps are involved: Mixing magnesium oxide and water, and performing ultrasonic stirring or ultra-long stirring to obtain magnesium oxide slurry; The magnesium oxide is analytical pure magnesium oxide, industrial purity 85% magnesium oxide, industrial purity 95.4% magnesium oxide or industrial purity 90% magnesium oxide; The ultra-long stirring time is ≥48h; When the magnesium oxide is analytically pure magnesium oxide, the ultra-long stirring time is ≥ 2h; The magnesium oxide slurry and the rare earth leaching mother solution are mixed and subjected to precipitation reaction under stirring conditions to obtain a mixed slurry; The mixed slurry is separated into solid and liquid to obtain a rare earth enriched product.

2. The method according to claim 1, characterized in that The particle size of the magnesium oxide is 200-250 meshes.

3. The method according to claim 1 or 2, characterized in that: The activity of the magnesium oxide is 65-80%.

4. The method according to claim 1 or 2, characterized in that: The mass ratio of the magnesium oxide to the rare earth in the rare earth leaching mother solution is 1.2-2.1:

1.

5. The method according to claim 1 or 2, characterized in that: The concentration of magnesium oxide in the magnesium oxide slurry is 5-20 g / L.

6. The method according to claim 1, characterized in that The ultrasonic power of the ultrasonic stirring is 80-100 Hz; the time of the ultrasonic stirring is 2-3 hours.

7. The method according to claim 1, characterized in that The rotation speed of the ultra-long time stirring is 600-800 rpm.

8. The method according to claim 1, characterized in that The mass concentration of rare earth in the rare earth leaching mother solution is 0.24-0.44 g / L.

9. The method according to claim 1, characterized in that: The stirring speed is 600-800 rpm; the stirring time is 1-3 hours.

10. The method according to claim 1, characterized in that After the solid-liquid separation, the method further comprises: drying the solid obtained by the solid-liquid separation to obtain a rare earth enriched product; the drying temperature is 100 to 110° C.; and the drying time is 7 to 10 hours.

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