CN108531735B - Method for extracting rare earth oxide from polishing powder waste - Google Patents
Method for extracting rare earth oxide from polishing powder waste Download PDFInfo
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- CN108531735B CN108531735B CN201810367237.1A CN201810367237A CN108531735B CN 108531735 B CN108531735 B CN 108531735B CN 201810367237 A CN201810367237 A CN 201810367237A CN 108531735 B CN108531735 B CN 108531735B
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
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Abstract
The application provides a method for extracting rare earth oxide from polishing powder waste, which comprises the following steps: dissolving, evaporating to remove impurities, extracting to remove impurities, washing to remove impurities, back-extracting and firing. According to the method for extracting the rare earth oxide from the polishing powder waste, the rare earth in the polishing powder waste can be separated from impurities such as silicon, aluminum, fluorine, calcium, magnesium and the like, the recovery rate of the rare earth can be effectively improved, ammonia water is not used in the whole process, and the requirement of environmental protection is met.
Description
Technical Field
The invention relates to the technical field of nonferrous metals, in particular to a method for extracting rare earth oxide from polishing powder waste.
Background
The polishing powder waste in the market is up to tens of thousands of tons, contains more than 65 percent of lanthanum-cerium mixed rare earth oxide, is a precious renewable resource, is beneficial to resource utilization and environmental protection if being recycled, and accords with the national industrial policy. The traditional method for recovering valuable rare earth from polishing powder waste mainly comprises roasting, alkaline leaching, purifying and impurity removing, extracting, separating and purifying. The method generally has the problems of low rare earth leaching yield, environmental pollution caused by the fact that chemical raw materials used for recovering rare earth are finally discharged by ammonia water and the like, so that the method is difficult to meet the requirement of a polishing powder waste recovery process. Therefore, it is a hot point of research for people to find a method for extracting rare earth oxide from polishing powder waste, which can improve the recovery rate of rare earth in the polishing powder waste and meet the requirements of green and environment-friendly production.
Disclosure of Invention
Based on the above, there is a need for a method for extracting rare earth oxide from polishing powder waste, which can improve the recovery rate of rare earth in the polishing powder waste and meet the requirement of green and environmental-friendly production
A method for extracting rare earth oxide from polishing powder waste comprises the following steps:
dissolving the polishing powder waste in first hydrochloric acid to obtain mother liquor containing rare earth elements;
evaporating and concentrating the mother liquor containing the rare earth elements, mixing the mother liquor with water, and carrying out solid-liquid separation to obtain the mother liquor containing the rare earth elements after impurity removal;
adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1-3, adding an organic extractant for extraction, standing for layering, and taking an organic phase to obtain an extraction liquid containing the rare earth elements;
washing the extraction liquid containing the rare earth elements by using second hydrochloric acid, standing for layering, and taking an organic phase to obtain an extraction liquid containing the rare earth elements after impurity removal;
carrying out back extraction on the extraction liquid containing the rare earth elements after impurity removal by using a third hydrochloric acid, standing and layering, and taking a water phase to obtain a back extraction liquid containing the rare earth elements;
and evaporating and concentrating the back extraction solution containing the rare earth elements, adjusting the pH value to 1.5-2, adding oxalic acid, filtering, and then firing to obtain the rare earth oxide.
In one embodiment, the temperature for dissolving the polishing powder waste in the first hydrochloric acid is 90-100 ℃; the mass ratio of the polishing powder waste to the first hydrochloric acid is 1 (1.5-3); the molar concentration of the hydrogen chloride in the first hydrochloric acid is 10-12 mol/L.
In one embodiment, the temperature for evaporating and concentrating the mother liquor containing the rare earth elements is 50-70 ℃.
In one embodiment, the reagent used for adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1-3 is fourth hydrochloric acid; the molar concentration of the hydrogen chloride in the fourth hydrochloric acid is 0.5-1 mol/L.
In one embodiment, the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is (1-3): 1, the organic extracting agent is a mixed solution of organic phosphate and kerosene, the organic phosphate is at least one selected from diisooctyl phosphate and diisooctyl isooctyl phosphate, and the volume ratio of the organic phosphate to the kerosene is (30-50): (50-70).
In one embodiment, before the step of adding the organic extractant for extraction, a step of saponifying the organic extractant is further included, and the saponification rate of the saponified organic extractant is 30% to 40%.
In one embodiment, the molar concentration of hydrogen chloride in the second hydrochloric acid is 0.2-0.5 mol/L, and the volume ratio of the rare earth element-containing extract to the second hydrochloric acid is (2-1): 1.
In one embodiment, the molar concentration of hydrogen chloride in the third hydrochloric acid is 2-4 mol/L, and the volume ratio of the rare earth element-containing extract subjected to impurity removal to the third hydrochloric acid is (2-1): 1.
In one embodiment, the reagent for adjusting the pH value to 1.5-2 is water.
In one embodiment, the condition of the burning is: firing at 800-900 deg.c for 2-4 hr.
According to the method for extracting the rare earth oxide from the polishing powder waste, the rare earth in the polishing powder waste can be separated from impurities such as silicon, aluminum, fluorine, calcium, magnesium and the like, the recovery rate of the rare earth can be effectively improved, ammonia water is not used in the whole process, and the requirement of environmental protection is met.
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FIG. 1 is a schematic flow chart illustrating a method for extracting rare earth oxide from polishing powder waste according to an embodiment.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, a method for extracting rare earth oxide from polishing powder waste according to an embodiment includes the following steps S110 to S160:
s110, dissolving: and dissolving the polishing powder waste in first hydrochloric acid to obtain mother liquor containing rare earth elements.
In the present embodiment, the polishing powder waste contains: rare Earth Oxide (REO), aluminum oxide (Al)2O3) Silicon oxide (SiO)2) Magnesium oxide (MgO), fluorine (F) and calcium oxide (CaO).
Wherein the temperature of the polishing powder waste dissolved in the first hydrochloric acid is 90-100 ℃. The time for dissolving the polishing powder waste in the first hydrochloric acid is 2-3 hours.
It can be understood that if the dissolving time is too short, the reaction is not thorough, and the yield of rare earth is reduced; if the dissolution time is too long, the acid is quickly evaporated to dryness, so that splashing accidents are easily caused, and the rare earth loss is caused.
Further, the mass ratio of the polishing powder waste to the first hydrochloric acid is 1 (1.5-3).
It will be appreciated that the first hydrochloric acid is an aqueous solution of hydrogen chloride. The molar concentration of the hydrogen chloride in the first hydrochloric acid is 10 mol/L-12 mol/L.
S120, evaporation and impurity removal: and (3) evaporating and concentrating the mother liquor containing the rare earth elements, mixing the mother liquor with water, and carrying out solid-liquid separation to obtain the mother liquor containing the rare earth elements after impurity removal.
Specifically, the mother liquor containing the rare earth elements is evaporated and concentrated to be nearly dry, and is mixed with water after being cooled, so that the crystal can be prevented from splashing, and safety accidents are avoided.
Wherein the temperature for evaporating and concentrating the mother liquor containing the rare earth elements is 50-70 ℃.
The mother liquor containing the rare earth elements is evaporated and concentrated to be nearly dry at the temperature of 50-70 ℃, and redundant acid, fluorine and silicon impurities in the rare earth solution can be effectively removed.
Further, the mass ratio of the polishing powder waste to the water is 1: 4. it will be appreciated that the water is preferably hot water in order to increase the solubility of the salts in the water.
Further, the solid-liquid separation mode is filter pressing.
It will be appreciated that the salts may be dissolved in water by mixing with water, leaving the remaining silicon impurities in the residue to be removed by solid-liquid separation.
S130, extraction and impurity removal: and adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1-3, adding an organic extractant for extraction, standing for layering, and taking an organic phase to obtain an extraction liquid containing the rare earth elements.
And adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1-3, wherein the used reagent is fourth hydrochloric acid.
It will be appreciated that the fourth hydrochloric acid is an aqueous solution of hydrogen chloride. The molar concentration of the hydrogen chloride in the fourth hydrochloric acid is 0.5 mol/L-1 mol/L.
Further, the steps of adding the organic extracting agent for extraction are as follows: adding an organic extractant to extract for 2-3 times.
Further, the organic extracting agent is a mixed solution of organic phosphate and kerosene. Wherein the organic phosphate is at least one of diisooctyl phosphate and diisooctyl isooctyl phosphate.
Further, the volume ratio of the organic phosphate to the kerosene is as follows: (30 to 50) and (50 to 70).
Further, the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is as follows: (1-3) 1.
In this embodiment, the method for extracting rare earth oxide from polishing powder waste further comprises a step of saponifying the organic extractant before the step of adding the organic extractant for extraction.
Specifically, the organic extractant is saponified with an aqueous sodium hydroxide solution having a molar concentration of 8 to 12 mol/L.
The saponification rate of the saponified organic extractant is 30-40%.
Note that saponification is to control the pH range of the organic extractant. If the saponification rate is more than 40%, the pH value of the organic extractant is higher, the extraction rates of aluminum, calcium, magnesium and rare earth are greatly improved, the purpose of separating the rare earth from the aluminum, calcium and magnesium cannot be achieved, and meanwhile, the problems of difficult phase separation and low rare earth yield caused by high saponification rate, easy emulsification of organic compatibility are also caused. If the saponification rate is less than 30%, the organic extractant has a low pH value, and aluminum, calcium, and magnesium are difficult to extract by the organic extractant, but the extraction rate of rare earth is also decreased, resulting in a low rare earth yield and an increased loss.
Through the extraction and impurity removal steps, the rare earth is extracted into an organic phase, and most of impurities such as aluminum, calcium, magnesium and the like are left in a water phase and are discharged into a sewage station for treatment.
S140, washing and impurity removal: washing the extraction liquid containing the rare earth elements with second hydrochloric acid, standing for layering, and taking an organic phase to obtain the extraction liquid containing the rare earth elements after impurity removal.
Wherein the rare earth element-containing extract is washed with the second hydrochloric acid 2-3 times.
It is understood that the second hydrochloric acid is an aqueous solution of hydrogen chloride. The molar concentration of the hydrogen chloride in the second hydrochloric acid is 0.2 mol/L-0.5 mol/L.
Further, the volume ratio of the rare earth element-containing extract to the second hydrochloric acid is: (2-1): 1.
Further, the stirring time is 30-40 minutes, and the standing time is 60-90 minutes.
And washing the extraction liquid containing the rare earth elements by using second hydrochloric acid, namely back-extracting impurities such as aluminum, calcium and magnesium, fluorine, sodium and the like in the extraction liquid containing the rare earth elements into a water phase, and discharging the water phase into a sewage station for treatment.
The number of washing the rare earth element-containing extract with the second hydrochloric acid is not limited to 2 to 3 times, as long as the impurities such as aluminum, calcium, and magnesium, fluorine, and sodium in the rare earth element-containing extract can be back-extracted.
S150, back extraction: and (3) performing back extraction on the extraction liquid containing the rare earth elements after impurity removal by using a third hydrochloric acid, standing and layering, and taking a water phase to obtain a back extraction liquid containing the rare earth elements.
It will be appreciated that the third hydrochloric acid is an aqueous solution of hydrogen chloride. The molar ratio of the hydrogen chloride in the third hydrochloric acid is 2 mol/L-4 mol/L.
Further, the volume ratio of the extraction liquid containing the rare earth elements after impurity removal to the third hydrochloric acid is as follows: (2-1): 1.
Further, the stirring time is 30-60 minutes, and the standing time is 60-90 minutes.
Through the back extraction step, the rare earth in the extraction liquid containing the rare earth elements after impurity removal can be back extracted into the water phase.
S160, firing: and (3) evaporating and concentrating the back extraction solution containing the rare earth elements, adjusting the pH value to 1.5-2, adding oxalic acid, filtering, and then firing to obtain the rare earth oxide.
Wherein the reagent for adjusting the pH value to 1.5-2 is water.
Further, the burning conditions are as follows: firing at 800-950 ℃ for 2-4 hours.
Through detection, in the rare earth oxide obtained by the method, REO is more than or equal to 99.0 percent, and Al2O3≤0.0025％，SiO2≤0.0020％，F≤0.0015％，CaO≤0.0035％，MgO≤0.0020％。
The method for extracting the rare earth oxide from the polishing powder waste can separate the rare earth from impurities such as silicon, aluminum, fluorine, calcium, magnesium and the like in the polishing powder waste, the process condition is easy to control, the recovery rate of the rare earth can reach more than 90 percent, ammonia water is not used in the whole process, and the requirement of environmental protection is met.
The following are specific examples.
Example 1
1. Dissolving: 100g of polishing powder waste (64.4 wt% REO, 2.44 wt% Al)2O313.32% by weight of SiO20.23% of MgO, 5.53% of F and 0.82% of CaO) was added to 150g of a first hydrochloric acid having a molar concentration of 10mol/L, heated to 90 ℃ and dissolved with stirring for 2 hours to obtain a mother liquor containing a rare earth element.
2. Evaporation and impurity removal: evaporating and concentrating the mother liquor containing the rare earth elements at 50 ℃ until the mother liquor is nearly dry, cooling, adding 400g of hot water, stirring, dissolving, and performing filter pressing to obtain the mother liquor containing the rare earth elements after impurity removal.
3. And (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1 by using 0.5mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 2 times (wherein the volume ratio of the organic extracting agent to the rare earth solution after impurity removal is 1:1), stirring for 30 minutes, standing for layering for 60 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extracting agent is a mixed solution of diisooctyl isooctyl phosphate and kerosene, and the volume ratio of the diisooctyl isooctyl phosphate to the kerosene is 30:70, the saponification rate of the organic extractant is 30%, and the molar concentration of the sodium hydroxide solution used for saponification is 8 mol/L.
4. Washing to remove impurities: washing the extraction liquid containing the rare earth elements for 2 times by using 0.2mol/L second hydrochloric acid (the volume ratio of the extraction liquid containing the rare earth elements to the second hydrochloric acid is 2:1), stirring for 30 minutes, standing and layering for 60 minutes to obtain the extraction liquid containing the rare earth elements after impurity removal.
5. Back extraction: and (3) performing back extraction on the impurity-removed extraction liquid containing the rare earth element by using 2mol/L third hydrochloric acid (the volume ratio of the impurity-removed extraction liquid containing the rare earth element to the third hydrochloric acid is 2:1), stirring for 30 minutes, standing and layering for 60 minutes to obtain back extraction liquid containing the rare earth element.
6. Firing: evaporating and concentrating the back extraction solution containing the rare earth elements, adding water to adjust the pH value to 1.5, adding oxalic acid, filtering and then firing to obtain the rare earth oxide.
The rare earth oxide obtained in example 1 was found to contain 99.05 wt% REO, 0.0020 wt% Al, 0.0015 wt% Si, 0.0018 wt% Mg, 0.0010 wt% F and 0.0027 wt% Ca. The yield of rare earth oxide was 90.17%.
Example 2
1. Dissolving: 100g of a polishing powder waste (containing 64.4 wt% of REO and 2.44 wt% of Al)2O313.32% by weight of SiO20.23% of MgO, 5.53% of F and 0.82% of CaO) was added to 300g of a first hydrochloric acid having a molar concentration of 12mol/L, heated to 100 ℃ and dissolved with stirring for 2 hours to obtain a mother liquor containing a rare earth element.
2. Evaporation and impurity removal: evaporating and concentrating the mother liquor containing the rare earth elements at 70 ℃ until the mother liquor is nearly dry, cooling, adding 400g of hot water, stirring, dissolving, and carrying out filter pressing to obtain the mother liquor containing the rare earth elements after impurity removal.
3. And (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 3 by using 1mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 3 times (wherein the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is 3:1), stirring for 40 minutes, standing for layering for 90 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extractant is a mixed solution of diisooctyl isooctyl phosphate and kerosene, the volume ratio of diisooctyl isooctyl phosphate to kerosene is 50:50, the saponification rate of the organic extractant is 40%, and the molar concentration of a sodium hydroxide solution used for saponification is 10 mol/L.
4. Washing to remove impurities: and (3) washing the extraction liquid containing the rare earth element for 3 times by using 0.5mol/L second hydrochloric acid (the volume ratio of the extraction liquid containing the rare earth element after impurity removal to the second hydrochloric acid is 2:1), stirring for 40 minutes, standing and layering for 90 minutes to obtain the extraction liquid containing the rare earth element after impurity removal.
5. Back extraction: and (3) performing back extraction on the impurity-removed extraction liquid containing the rare earth element by using 4mol/L third hydrochloric acid (the volume ratio of the impurity-removed extraction liquid containing the rare earth element to the third hydrochloric acid is 1:1), stirring for 40 minutes, standing and layering for 90 minutes to obtain back extraction liquid containing the rare earth element.
6. Firing: evaporating and concentrating the back extraction solution containing the rare earth elements, adding water to adjust the pH value to 2, adding oxalic acid, filtering and then firing to obtain the rare earth oxide.
The rare earth oxide obtained in example 2 was found to contain 99.27 wt% REO, 0.0024 wt% Al, 0.0020 wt% Si, 0.0020 wt% Mg, 0.0015 wt% F and 0.0035 wt% Ca. The yield of rare earth oxide was 92.34%.
Example 3
Example 3 is essentially the same as example 1, except that the dissolution step of example 3 is:
dissolving: 100g of a polishing powder waste (containing 64.4 wt% of REO and 2.44 wt% of Al)2O313.32% by weight of SiO20.23% of MgO, 5.53% of F and 0.82% of CaO) was added to 250g of a first hydrochloric acid having a molar concentration of 9mol/L, heated to 90 ℃ and dissolved with stirring for 2 hours to obtain a mother liquor containing a rare earth element.
The rare earth oxide obtained in example 3 was found to contain 99.15 wt% REO, 0.0017 wt% Al, 0.0014 wt% Si, 0.0020 wt% Mg, 0.0011 wt% F and 0.0025 wt% Ca. The yield of the rare earth oxide was 91.15%.
Example 4
Example 4 is essentially the same as example 1, except that the dissolution step and the evaporation impurity removal step of example 4 are:
1. dissolving: 100g of a polishing powder waste (containing 64.4 wt% of REO and 2.44 wt% of Al)2O313.32% by weight of SiO20.23% of MgO, 5.53% of F and 0.82% of CaO) was added to 150g of a first hydrochloric acid having a molar concentration of 10mol/L, heated to 90 ℃ and dissolved with stirring for 3 hours to obtain a mother liquor containing a rare earth element.
2. And (3) evaporating and concentrating the mother liquor containing the rare earth elements at 70 ℃ until the mother liquor is nearly dry, adding 400g of hot water, stirring and dissolving, and then carrying out filter pressing to obtain the mother liquor containing the rare earth elements after impurity removal.
As a result of examination, the rare earth oxide obtained in example 4 contained 99.10 wt% of REO, 0.0018 wt% of Al, 0.0014 wt% of Si, 0.0017 wt% of Mg, 0.0011 wt% of F and 0.0030 wt% of Ca. The yield of rare earth oxide was 90.48%.
Example 5
Example 5 is essentially the same as example 1, except that the extractive stripping step of example 5 is:
and (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 3 by using 1mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 3 times (wherein the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is 3:1), stirring for 40 minutes, standing for layering for 90 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extractant is a mixed solution of diisooctyl isooctyl phosphate and kerosene, the volume ratio of diisooctyl isooctyl phosphate to kerosene is 50:50, the saponification rate of the organic extractant is 40%, and the molar concentration of a sodium hydroxide solution used for saponification is 10 mol/L.
The rare earth oxide obtained in example 5 was found to contain 99.00 wt% REO, 0.0023 wt% Al, 0.0017 wt% Si, 0.0019 wt% Mg, 0.0014 wt% F and 0.0034 wt% Ca. The yield of rare earth oxide was 92.04%.
Example 6
Example 6 is essentially the same as example 1, except that the stripping step of example 6 is:
back extraction: and (3) performing back extraction on the impurity-removed extraction liquid containing the rare earth element by using 1mol/L third hydrochloric acid (the volume ratio of the impurity-removed extraction liquid containing the rare earth element to the third hydrochloric acid is 3:1), stirring for 30 minutes, standing and layering for 60 minutes to obtain back extraction liquid containing the rare earth element.
The rare earth oxide obtained in example 6 was found to contain 99.02 wt% REO, 0.0017 wt% Al, 0.0016 wt% Si, 0.0015 wt% Mg, 0.0013 wt% F and 0.0025 wt% Ca. The yield of rare earth oxide was 68.12%.
Example 7
Example 7 is essentially the same as example 1, except that the evaporation impurity removal step of example 7 is:
evaporation and impurity removal: evaporating and concentrating the mother liquor containing the rare earth elements at 40 ℃ until the mother liquor is nearly dry, cooling, adding 400g of hot water, stirring, dissolving, and performing filter pressing to obtain the mother liquor containing the rare earth elements after impurity removal.
The rare earth oxide obtained in example 7 was found to contain 99.00 wt% REO, 0.0017 wt% Al, 0.025 wt% Si, 0.0020 wt% Mg, 0.035 wt% F and 0.0030 wt% Ca. The yield of rare earth oxide was 91.52%.
Example 8
Example 8 is essentially the same as example 1, except that the evaporation impurity removal step of example 8 is:
evaporation and impurity removal: evaporating and concentrating the mother liquor containing the rare earth elements at 90 ℃ until the mother liquor is nearly dry, cooling, adding 400g of hot water, stirring, dissolving, and performing filter pressing to obtain the mother liquor containing the rare earth elements after impurity removal.
The rare earth oxide obtained in example 8 was found to contain 99.21 wt% REO, 0.0015 wt% Al, 0.0021 wt% Si, 0.0017 wt% Mg, 0.0012 wt% F and 0.0018 wt% Ca. The yield of rare earth oxide was 85.21%.
Example 9
Example 9 is essentially the same as example 1 except that the extractive stripping step of example 9 is:
and (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1 by using 0.5mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 2 times (wherein the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is 1:1), stirring for 30 minutes, standing for layering for 60 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extracting agent is a mixed solution of diisooctyl isooctyl phosphate and kerosene, and the volume ratio of the diisooctyl isooctyl phosphate to the kerosene is 30:70, the saponification rate of the organic extractant is 50%, and the molar concentration of the sodium hydroxide solution used for saponification is 8 mol/L.
The rare earth oxide obtained in example 9 was found to contain 97.21 wt% REO, 0.012 wt% Al, 0.0020 wt% Si, 0.10 wt% Mg, 0.0014 wt% F and 0.24 wt% Ca. The yield of the rare earth oxide was 90.05%.
Example 10
Example 10 is essentially the same as example 1, except that the extraction and impurity removal step of example 10 is:
and (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1 by using 0.5mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 2 times (wherein the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is 1:1), stirring for 30 minutes, standing for layering for 60 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extracting agent is a mixed solution of diisooctyl isooctyl phosphate and kerosene, and the volume ratio of the diisooctyl isooctyl phosphate to the kerosene is 30: 70.
The rare earth oxide obtained in example 10 was found to contain 93.15 wt% REO, 0.0015 wt% Al, 0.0015 wt% Si, 0.0012 wt% Mg, 0.0010 wt% F and 0.0016 wt% Ca. The yield of the rare earth oxide was 5.45%.
Comparative example 1
Comparative example 1 is substantially the same as example 1 except that the extraction and impurity removal step of comparative example 1 is:
and (3) extraction and impurity removal: and (3) adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 4 by using 0.5mol/L fourth hydrochloric acid, adding an organic extracting agent for extraction for 2 times (wherein the volume ratio of the organic extracting agent to the mother liquor containing the rare earth elements after impurity removal is 1:1), stirring for 30 minutes, standing for layering for 60 minutes, and taking an organic phase to obtain an extraction liquid containing the rare earth elements. Wherein the organic extracting agent is a mixed solution of diisooctyl isooctyl phosphate and kerosene, and the volume ratio of the diisooctyl isooctyl phosphate to the kerosene is 30:70, the saponification rate of the organic extractant is 30%, and the molar concentration of the sodium hydroxide solution used for saponification is 8 mol/L.
The rare earth oxide obtained in example 1 was found to contain 96.25 wt% REO, 0.015 wt% Al, 0.0023 wt% Si, 0.12 wt% Mg, 0.0017 wt% F and 0.27 wt% Ca. The yield of rare earth oxide was 90.17%.
Comparative example 2
Comparative example 2 is substantially the same as example 1 except that comparative example 2 has the burning step of:
firing: evaporating and concentrating the back extraction solution containing the rare earth elements, adding water to adjust the pH value to 4, adding oxalic acid, filtering and then firing to obtain the rare earth oxide.
It was detected that the rare earth oxide obtained in comparative example 2 contained 99.13 wt% REO, 0.025 wt% Al, 0.0021 wt% Si, 0.014 wt% Mg, 0.0016 wt% F and 0.028 wt% Ca. The yield of the rare earth oxide was 91.12%.
Comparative example 3
Comparative example 3 is substantially the same as example 1 except that comparative example 3 omits the step of washing to remove impurities.
It was found that the rare earth oxide obtained in comparative example 5 contained 87.65 wt% of REO, 0.027 wt% of Al, 0.43 wt% of Si, 0.12 wt% of Mg, 0.015 wt% of F, and 0.23 wt% of Ca. The yield of rare earth oxide was 93.21%.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for extracting rare earth oxide from polishing powder waste is characterized by comprising the following steps:
dissolving the polishing powder waste in first hydrochloric acid to obtain mother liquor containing rare earth elements; the temperature for dissolving the polishing powder waste in the first hydrochloric acid is 90-100 ℃, and the molar concentration of hydrogen chloride in the first hydrochloric acid is 10-12 mol/L;
evaporating and concentrating the mother liquor containing the rare earth elements to be nearly dry, mixing the mother liquor with water, and carrying out solid-liquid separation to obtain the mother liquor containing the rare earth elements after impurity removal;
adjusting the pH value of the mother liquor containing the rare earth elements after impurity removal to 1-3, adding an organic extractant for extraction, standing for layering, and taking an organic phase to obtain an extraction liquid containing the rare earth elements;
washing the extraction liquid containing the rare earth elements by using second hydrochloric acid, standing for layering, and taking an organic phase to obtain an extraction liquid containing the rare earth elements after impurity removal; the molar concentration of hydrogen chloride in the second hydrochloric acid is 0.2-0.5 mol/L;
carrying out back extraction on the rare earth element-containing extract liquor after impurity removal by using third hydrochloric acid, standing and layering, and taking a water phase to obtain a back extract liquor containing the rare earth element, wherein the molar concentration of hydrogen chloride in the third hydrochloric acid is 2-4 mol/L;
and evaporating and concentrating the back extraction solution containing the rare earth elements, adjusting the pH value to 1.5-2, adding oxalic acid, filtering, and then firing to obtain the rare earth oxide.
2. The method for extracting rare earth oxide from polishing powder waste according to claim 1, wherein the mass ratio of the polishing powder waste to the first hydrochloric acid is 1 (1.5-3).
3. The method for extracting rare earth oxide from polishing powder waste as claimed in claim 1, wherein the temperature for evaporating and concentrating the mother liquor containing rare earth element is 50 ℃ to 70 ℃.
4. The method for extracting rare earth oxide from polishing powder waste according to claim 1, wherein the reagent for adjusting the pH of the impurity-removed mother liquor containing rare earth element to 1 to 3 is fourth hydrochloric acid; the molar concentration of the hydrogen chloride in the fourth hydrochloric acid is 0.5-1 mol/L.
5. The method for extracting rare earth oxide from polishing powder waste according to claim 1 or 4, wherein the volume ratio of the organic extractant to the mother solution containing rare earth element after impurity removal is (1-3): 1, the organic extractant is a mixed solution of organic phosphate and kerosene, the organic phosphate is diisooctyl phosphate, and the volume ratio of the organic phosphate to the kerosene is (30-50): (50-70).
6. The method of claim 1, further comprising a step of saponifying the organic extractant before the step of adding the organic extractant, wherein the saponification rate of the saponified organic extractant is 30% to 40%.
7. The method for extracting rare earth oxide from polishing powder waste according to claim 1, wherein the volume ratio of the rare earth element-containing extract to the second hydrochloric acid is (2-1): 1.
8. The method for extracting rare earth oxide from polishing powder waste according to claim 1, wherein the volume ratio of the impurity-removed rare earth element-containing extract to the third hydrochloric acid is (2-1): 1.
9. The method for extracting rare earth oxide from polishing powder waste according to claim 1, wherein the reagent for adjusting the pH to 1.5 to 2 is water.
10. The method for extracting rare earth oxide from polishing powder waste as claimed in claim 1, wherein the firing conditions are: firing at 800-900 deg.c for 2-4 hr.
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