CN111170352B - Method for preparing rare earth fluoride particles by using fluorine-containing waste acid - Google Patents
Method for preparing rare earth fluoride particles by using fluorine-containing waste acid Download PDFInfo
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Abstract
The invention discloses a method for preparing rare earth fluoride particles by using fluorine-containing waste acid, which comprises the following steps: (1) Dripping the fluorine-containing waste acid and the rare earth metal salt aqueous solution into the base solution in a parallel flow manner for reaction to obtain a reaction solution; (2) Solid-liquid separation is carried out on the reaction liquid to obtain rare earth fluoride precipitate and mother liquor containing acid radical ions A; drying and roasting the rare earth fluoride precipitate to obtain rare earth fluoride particles; (3) And (3) adjusting the hydrogen ion concentration of the mother liquor containing the acid radical ions A by adopting acid containing the acid radical ions A to obtain solution B, and treating the rare earth raw material by using the solution B as a back extraction solution to form the rare earth metal salt aqueous solution. The method can realize high-value utilization of the fluorine-containing waste acid, and the obtained product has large particle size, is easy to filter and has high fluorine conversion rate.
Description
Technical Field
The invention relates to a method for preparing rare earth fluoride particles by using fluorine-containing waste acid.
Background
The content of fluorine resources in the crust is 0.072%, mainly from fluorite, phosphate ore, etc. The demand for fluorine resources from rapidly developing industries is increasing, and the shortage of fluorite, phosphate ore and the like is inevitably caused. Therefore, attention is paid to the comprehensive recovery and high-value utilization of fluorine-containing by-products (especially fluorine-containing waste acid) in the fluorine chemical process.
On the one hand, the rare earth fluoride is an important raw material and electrolyte for preparing rare earth metals and alloys, and is also an important additive in steel and nonferrous metals. The rare earth fluoride can also be used as a rare earth polishing powder additive, a carbon arc rod luminous agent, fluoride optical fiber, fluorescent powder and the like. The production and application of the rare earth fluoride are very important, so that the conversion of the fluorine-containing waste acid which is a byproduct in the fluorine chemical process into the rare earth fluoride belongs to high-value conversion and utilization.
The conventional preparation method of the rare earth fluoride comprises a wet process and a dry process. The dry process is carried out at high temperature, the rare earth oxide is fluorinated by adopting hydrogen fluoride gas, and anhydrous rare earth fluoride products can be directly synthesized. However, the method has extremely high corrosion prevention requirements on equipment, low utilization rate of hydrogen fluoride and high fluorination cost. The wet process includes two processes. A wet process for preparing the ammonium salt-type sewage features that the soluble rare-earth metal salt is directly converted with hydrofluoric acid or acidic ammonium bifluoride to obtain the rare-earth fluoride whose particles are fine, colloidal and difficult to filter, and the ammonia water is used for neutralizing to obtain the ammonium salt-type sewage. In another wet process, acid composite fluorinating agent is used to react with rare earth carbonate and rare earth oxalate to produce rare earth fluoride with large granularity and easy filtration. However, the method still uses ammonia water to neutralize the fluoric acid in advance, and the recycling of the acid in the mother liquor cannot be well realized.
CN1048531A discloses a preparation method of rare earth metal fluoride, taking soluble rare earth metal salt aqueous solution, rare earth oxide, oxalic acid rare earth metal salt, ammonium sulfate rare earth complex salt or slurry of acid carbonic acid rare earth metal salt as raw material solution, firstly adding oxalic acid, then adding hydrofluoric acid, and carrying out solid-liquid separation to obtain the rare earth metal fluoride. The method firstly generates rare earth oxalate, and then hydrofluoric acid is added for fluorination. Therefore, the amount of oxalic acid used is large, and an excess of hydrofluoric acid needs to be used, and recycling of the acid-containing mother liquor is not mentioned.
CN101607733A discloses a method for preparing rare earth fluoride by using rare earth oxide as raw material. Mixing rare earth oxide with water, and adding concentrated hydrochloric acid to react to generate a rare earth chloride solution; heating the chlorinated rare earth solution to 70-90 ℃, adding malonic acid as a precipitator, and then preserving heat for 10-30 minutes; adding hydrofluoric acid into the reaction solution, and carrying out fluorination reaction at 70-90 ℃; and washing, settling, filtering and drying the precipitate generated by the reaction to obtain the rare earth fluoride. The above method uses malonic acid as a precipitant, not as an induced crystallization agent. Therefore, although the method can increase the size of the rare earth fluoride particles to some extent, it is disadvantageous to filtration because the method of precipitation followed by fluorination cannot exert the function of malonic acid induced crystallization, resulting in still small particle size of the rare earth fluoride particles. In addition, in the above method, hydrofluoric acid is used in a slight excess amount (the amount of hydrofluoric acid used is 101% to 105% of the theoretical amount thereof), and thus fluorine-containing waste water is generated. Although the hydrochloric acid-containing mother liquor obtained in this method is referred to as a recyclable one, hydrochloric acid in the mother liquor is a low-concentration acid, and the dissolution of rare earth oxides with the low-concentration acid has the following problems: firstly, the acid solubility of some rare earth oxides is poor, and the efficiency of dissolving with low-concentration acid is extremely low; secondly, the rare earth oxide prepared from the rare earth oxide is a waste of resources, because the rare earth oxide is formed by high-temperature firing after the rare earth salt solution is precipitated by ammonium bicarbonate or oxalic acid, a large amount of waste water is formed in the precipitation process, and the method is not environment-friendly.
On the other hand, the fluorine-containing waste acid which is a by-product in the fluorine chemical process is not utilized with high value. In the sulfuric acid smelting process of the fluorine-containing rare earth mineral, fluorine-containing substances enter tail gas in the form of hydrogen fluoride and silicon tetrafluoride, and after spraying and absorption, low-concentration fluorine-containing waste acid is formed. CN109384248A discloses a method for reducing ammonium fluosilicate in ammonium fluoride. The method comprises the steps of neutralizing fluosilicic acid (a byproduct in the production process of phosphate fertilizers) with ammonia to obtain a mixed solution containing silicon dioxide and ammonium fluoride, filtering the mixed solution containing the silicon dioxide and the ammonium fluoride through a filter press, standing, finely filtering, concentrating, introducing ammonia, crystallizing and centrifugally separating to obtain an ammonium fluoride product. The ammonium fluoride produced by the method is a conventional chemical product, and the added value is low, so that the utilization value of the raw material fluosilicic acid is low. CN101134595A discloses a production method of calcium fluoride. Reacting a fluosilicic acid (a byproduct in the production process of a phosphate fertilizer) solution with calcium oxide, and filtering to obtain a calcium fluosilicate solid after the reaction is finished; decomposing calcium fluorosilicate at 200-600 deg.c to produce solid calcium fluoride product and silicon tetrafluoride gas; absorbing and hydrolyzing the silicon tetrafluoride gas, and filtering to obtain a fluosilicic acid solution which is returned to prepare the calcium fluosilicate. Although the fluosilicic acid is recycled, the product of the method is used as a mineral raw material, and the high-value recycling of the fluosilicic acid is not realized.
In conclusion, how to produce the easily-filtered rare earth fluoride particles by using the fluorine-containing waste acid and realize the recycling of the acid-containing mother liquor is a problem to be solved urgently.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method for preparing rare earth fluoride particles using fluorine-containing waste acid. The method can realize high-value utilization of the fluorine-containing waste acid, and the obtained product rare earth fluoride has large particle size, is easy to filter and has high fluorine conversion rate. Further, the method can realize the recycling of the obtained mother liquor (namely the acid-containing mother liquor) containing the acid radical ions A.
The invention achieves the above purpose through the following technical scheme.
The invention provides a method for preparing rare earth fluoride particles by using fluorine-containing waste acid, which comprises the following steps:
(1) Dripping the fluorine-containing waste acid and the rare earth metal salt aqueous solution into the base solution in a parallel flow manner for reaction to obtain a reaction solution; wherein the rare earth metal salt contains an acid radical ion A; wherein, the fluorine-containing waste acid contains fluorinion, and the base solution is water or acid aqueous solution; the fluorine-containing waste acid and/or the base solution contains carboxylic acid or salt thereof capable of releasing free carboxylate radicals as a crystallization-inducing agent;
(2) Solid-liquid separation is carried out on the reaction liquid to obtain rare earth fluoride precipitate and mother liquor containing acid radical ions A; drying and roasting the rare earth fluoride precipitate to obtain rare earth fluoride particles; and
(3) And (3) adjusting the hydrogen ion concentration of the mother liquor containing the acid radical ions A by adopting acid containing the acid radical ions A to obtain solution B, and treating the rare earth raw material by using the solution B as a back extraction solution to form the rare earth metal salt aqueous solution.
According to the method of the present invention, preferably, the fluorine-containing waste acid is (1) a waste acid containing fluorosilicic acid, or (2) a waste acid containing hydrofluoric acid and fluorosilicic acid.
According to the method of the present invention, preferably, the fluorine-containing waste acid is (1) fluosilicic acid produced in phosphate fertilizer production, or (2) tail gas acid containing hydrofluoric acid and fluosilicic acid produced in a fluorine-containing rare earth mineral sulfuric acid smelting process.
According to the method of the present invention, preferably, the rare earth metal salt in the aqueous rare earth metal salt solution is selected from one of rare earth chlorides and rare earth nitrates.
The process according to the invention is preferably carried out with F - Calculated waste acid containing fluorine and RE 3+ The molar ratio of the rare earth metal salt in the rare earth salt water solution is 2.55-2.997.
According to the method of the present invention, it is preferable to control the relative dropping speeds of the fluorine-containing waste acid and the aqueous solution of a rare earth metal salt so as to be F during the concurrent dropping - Calculated fluorine-containing waste acid and RE 3+ The molar ratio of the rare earth metal salt in the rare earth salt water solution is 2-3.5.
According to the process of the present invention, preferably, the molar amount of the crystallization-inducing agent in terms of carboxylate groups is X, and the rare earth metal salt in the aqueous solution of the rare earth metal salt is RE 3+ Calculating the molar quantity of the needed carboxylate radical as Y according to the molecular stoichiometric ratio on the basis, and then the dosage of the induced crystallization agent conforms to the following formula:
X/Y＝0.1～15％。
according to the process of the present invention, preferably, the cocurrent dropwise addition is carried out at from 40 to 90 ℃.
According to the method of the present invention, preferably, the crystallization inducing agent is selected from one or more of oxalic acid, ammonium oxalate, sodium oxalate, rare earth oxalates, malonic acid, ammonium malonate, sodium malonate, propionic acid, ammonium propionate and sodium propionate.
According to the process of the present invention, preferably, the hydrogen ion concentration of the solution B is 5 to 10mol/L.
The method comprises the steps of dropwise adding fluorine-containing waste acid and rare earth metal salt aqueous solution into a base solution in a parallel flow manner for reaction, wherein the base solution and/or the fluorine-containing waste acid contain carboxylic acid or salt thereof capable of releasing free carboxylate radicals as an induced crystallization agent, so that rare earth fluoride particles and acid-containing mother solution are prepared, and the acid-containing mother solution is recycled. The method of the invention realizes high-value utilization of the fluorine-containing waste acid. The obtained rare earth fluoride particles have large particle size, are easy to filter and have high fluorine conversion rate. According to the preferable technical scheme, the method can realize the recycling of the mother liquor containing the acid radical ions A (namely the acid-containing mother liquor). According to a more preferred embodiment of the present invention, the particle size of the rare earth fluoride particles can be further increased by controlling the relative dropping rate during concurrent dropping.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
"d" of the invention 50 "median diameter" or "median diameter" means the diameter corresponding to the percentage of the cumulative particle size distribution of a sample that reaches 50%. Its physical meaning is that the particles have a size greater than 50% of its size and less than 50% of its size.
In the present invention, fluorine conversion = (in F) - Molar number of rare earth fluoride expressed as F - The mole number of the fluorine-containing waste acid) is multiplied by 100 percent. Fluorine conversion is synonymous with fluorine conversion.
The method of the invention comprises the following steps: (1) a parallel-flow dropwise adding step; (2) a reaction solution treatment step; and (3) recycling the mother liquor. The process flow diagram refers to fig. 1. As described in detail below.
< concurrent dropwise addition step >
And (3) dropwise adding the fluorine-containing waste acid and the rare earth metal salt aqueous solution into the base solution in a parallel flow manner to react to obtain a reaction solution. By utilizing the method, the problem of comprehensive utilization of the fluorine-containing waste acid is solved, and high-value utilization of the fluorine-containing waste acid is realized. In addition, the rare earth fluoride particles obtained by the method have large particle size, are easier to filter and have high fluorine conversion rate.
The fluorine-containing waste acid contains fluorine ions. Examples of the fluorine-containing waste acid include, but are not limited to, (1) waste acid containing fluorosilicic acid, or (2) waste acid of a mixed acid solution containing hydrofluoric acid and fluorosilicic acid. In the invention, the fluorine-containing waste acid can be (1) fluosilicic acid formed in phosphate fertilizer production, or (2) tail gas acid containing hydrofluoric acid and fluosilicic acid generated in a fluorine-containing rare earth mineral sulfuric acid smelting process. In the process of the sulfuric acid smelting process of the fluorine-containing rare earth mineral, fluorine ions enter tail gas in the form of hydrogen fluoride and silicon tetrafluoride, and after spraying and absorption, low-concentration fluorine-containing waste acid, namely tail gas acid, is formed. In the prior art, the by-product fluosilicic acid in phosphate fertilizer production is generally used for producing ammonium fluoride or calcium fluoride, and the waste fluosilicic acid cannot be used for producing products with high added value. The invention uses the fluorine-containing waste acid to produce the rare earth fluoride particles, so that the fluorine-containing waste acid is utilized with high value, the conversion rate of fluorine is high, and the obtained product has large particle size and is easy to filter. The fluorine-containing waste acid in the invention is preferably tail gas acid containing hydrofluoric acid and fluosilicic acid formed by a fluorine-containing rare earth mineral sulfuric acid smelting process. This is advantageous for increasing the particle size of the rare earth fluoride particles.
The aqueous solution of the rare earth metal salt can be an acidic aqueous solution or a neutral aqueous solution. The rare earth metal salt in the aqueous solution of the rare earth metal salt contains an acid radical ion A. The acid radical ion A may be chloride ion or nitrate ion. Specifically, the rare earth metal salt may be selected from one of rare earth chlorides and rare earth nitrates. Correspondingly, when the fluorine-containing waste acid and the rare earth metal salt are used for reaction, the obtained mother liquor is the mother liquor containing chloride ions or the mother liquor containing nitrate ions.
The rare earth element of the rare earth metal salt may be selected from at least one of lanthanum, cerium, yttrium, neodymium, praseodymium, dysprosium, and samarium. Of course, the rare earth element of the rare earth metal salt may not be limited thereto as long as a water-soluble rare earth metal salt can be formed. Examples of rare earth metal salts include, but are not limited to, lanthanum fluoride, cerium fluoride, lanthanum cerium chloride, yttrium nitrate, or neodymium nitrate.
In the present invention, the base solution is water or an acidic aqueous solution. The aqueous acidic solution may be dilute hydrochloric acid or dilute nitric acid. The concentration of the dilute hydrochloric acid or dilute nitric acid is 0.0001 to 15wt%, preferably 0.001 to 10wt%, more preferably 0.01 to 5wt%. In certain embodiments, the base solution may also be a washing liquid obtained by washing the rare earth fluoride precipitate (solid) with water at the time of the post-treatment. The amount of the base solution used in the present invention is not particularly limited. Preferably, the volume of the base liquid is equal to F - The molar ratio of the fluorine-containing waste acid is 30-550ml, more preferably 35-500ml, and still more preferably 40-450ml.
The fluorine-containing waste acid and/or the base solution contains carboxylic acid or salt thereof capable of releasing free carboxylate radical as crystallization inducing agent. In certain embodiments, the fluorine-containing waste acid contains an induced crystallization agent, and the base solution does not contain an induced crystallization agent. In other embodiments, the base solution contains an induced crystallization agent and the spent fluorine-containing acid does not contain an induced crystallization agent. This is advantageous for forming the rare earth fluoride particles having a large particle size.
In some embodiments, the crystallization-inducing agent of the present invention is a carboxylic acid capable of releasing a free carboxylate. The carboxylic acid capable of releasing a free carboxylate radical according to the invention may be a monocarboxylic acid, a dicarboxylic acid or a polycarboxylic acid, preferably a monocarboxylic acid or a dicarboxylic acid, more preferably oxalic acid, propionic acid or malonic acid. In other embodiments, the crystallization inducing agent of the present invention is a carboxylate salt capable of releasing a free carboxylate. The carboxylate of the present invention may be a monocarboxylate, a dicarboxylate or a polycarboxylate, preferably a monocarboxylate or dicarboxylate, more preferably an oxalate, propionate or malonate. Examples of carboxylates include, but are not limited to, oxalates, propionates, malonates, and the like. The carboxylate may be an alkali metal carboxylic acid or an ammonium carboxylate salt, and the like. The alkali metal in the alkali metal carboxylic acid may be sodium, potassium or the like, and sodium is preferred. The ammonium carboxylate salt may be ammonium oxalate, ammonium propionate or ammonium malonate. The oxalate may also be a rare earth oxalate in which the rare earth is of the same type as the rare earth in the aqueous rare earth metal salt solution. For example, if the rare earth in the aqueous rare earth metal salt solution is neodymium, the rare earth oxalate is neodymium oxalate. According to one embodiment of the invention, the crystallization inducing agent is selected from one or more of oxalic acid, ammonium oxalate, sodium oxalate, rare earth oxalates, malonic acid, ammonium malonate, sodium malonate, propionic acid, ammonium propionate and sodium propionate. Thus being beneficial to properly improving the particle size of the rare earth fluoride particles and avoiding the generation of colloidal substances.
The mol weight of the induced crystallization agent in terms of carboxylate radical is X, and the rare earth metal salt in the rare earth metal salt aqueous solution is RE 3+ Calculating the molar quantity of the needed carboxylate radical as Y according to the molecular stoichiometric ratio on the basis, and then the dosage of the induced crystallization agent conforms to the following formula: X/Y = 0.1-15%; preferably, X/Y = 0.5-15%; more preferably, X/Y =5.0 to 10.0%. Thus being beneficial to promoting the generation of rare earth fluoride particles with large particle size and being easy to filter.
With F - Calculated fluorine-containing waste acid and RE 3+ The molar ratio of the rare earth metal salt in the rare earth metal salt aqueous solution is 2.55-2.997, preferably 2.56-2.995. This is advantageous for reducing the fluorine content of the mother liquor.
Controlling the relative dropping speed of the fluorine-containing waste acid and the aqueous solution of the rare earth metal salt so that F is used in the concurrent dropping process - Calculated fluorine-containing waste acid and RE 3+ The molar ratio of the rare earth metal salt in the rare earth metal salt aqueous solution is 2-3.5. The particle size of the rare earth fluoride particles obtained in this way is large, and the conversion rate of fluorine is favorably improved.
According to an embodiment of the present invention, the rare earth metal salt in the rare earth metal salt aqueous solution is selected from one of rare earth chloride and rare earth nitrate; the fluorine-containing waste acid is (1) waste acid containing fluorine silicic acid, or (2) waste acid containing hydrofluoric acid and fluosilicic acid; the crystallization inducing agent is one or more selected from oxalic acid, ammonium oxalate, sodium oxalate, rare earth oxalate, malonic acid, ammonium malonate, sodium malonate, propionic acid, ammonium propionate and sodium propionate.
The parallel flow dripping process of the fluorine-containing waste acid and the rare earth metal salt aqueous solution can be carried out at the temperature of between 40 and 90 ℃. Preferably, the co-current dropwise addition process is carried out at 40 to 85 ℃. More preferably, the concurrent dropwise addition process is carried out at 40 to 80 ℃. This is beneficial to increase the conversion rate of fluorine and avoid the generation of colloidal substances. The temperature during the concurrent dropwise addition can be controlled in various ways, for example, the base solution is heated before the concurrent dropwise addition and then maintained in the above temperature range.
< step of treating reaction solution >
Carrying out solid-liquid separation on the reaction solution to obtain rare earth fluoride precipitate and mother solution containing acid radical ions A; and drying and roasting the rare earth fluoride precipitate to obtain rare earth fluoride particles.
In the present invention, the solid-liquid separation may be performed by centrifugation or filtration. Because the particle size of the rare earth fluoride particles obtained by the method is larger, the method can adopt centrifugation or filtration. Solid-liquid separation is preferably carried out by adopting a filtration mode, so that continuous production is easy to realize.
The kind of the acid radical ion A is the same as that of the rare earth metal salt in the rare earth metal salt aqueous solution. For example, if the rare earth metal salt is a rare earth chloride, the acid ion A is a chloride ion. For another example, if the rare earth metal salt is a rare earth nitrate, the acid radical ion a is a nitrate radical ion.
In the invention, the mother liquor containing acid radical ions A is acid-containing mother liquor. The mother liquor containing chloride ions is the mother liquor containing hydrochloric acid, and the mother liquor containing nitrate ions is the mother liquor containing nitric acid. The hydrogen ions in the acid-containing mother liquor are from hydrogen ions in the fluorine-containing waste acid. In the present invention, the concentration of the acid (i.e., hydrogen ion concentration) in the resulting mother liquor is not less than 1mol/L. The fluorine content in the obtained mother liquor is lower, and even fluorine-free mother liquor is obtained.
And drying and roasting the obtained rare earth fluoride precipitate. The drying temperature can be 100-180 ℃, and the drying time is 1-5 h. Preferably, the drying temperature is 105-170 ℃, and the drying time is 1.5-4.5 h. More preferably, the drying temperature is 110-160 ℃, and the drying time is 1.5-4 h. The roasting temperature can be 550-850 ℃, and the roasting time is 1-7 h. Preferably, the roasting temperature is 555-800 ℃, and the burning time is 1.5-6.5 h. More preferably, the roasting temperature is 560-750 ℃ and the roasting time is 1.5-6.0 h. In certain embodiments, prior to drying, the rare earth fluoride precipitate is washed with water to obtain a wash solution, which is recycled as a base solution.
< mother liquor Recycling step >
And (3) adjusting the hydrogen ion concentration of the mother liquor containing the acid radical ions A by adopting acid containing the acid radical ions A to obtain solution B, and treating the rare earth raw material by using the solution B as a back extraction solution to form the rare earth metal salt aqueous solution. Thus, the mother liquor containing acid radical ions A (namely, the acid-containing mother liquor) can be recycled, and the raw material rare earth metal salt aqueous solution of the invention can be obtained. By adopting the method, the discharge of industrial waste liquid is greatly reduced.
In the present invention, the acid used for the adjustment is preferably the same as the acid radical ion of the acid contained in the mother liquor. The mother liquor containing the chloride ions is adjusted in hydrogen ion concentration by hydrochloric acid. The mother liquor containing nitrate ions is adjusted to the hydrogen ion concentration with nitric acid. It is apparent that the hydrogen ion concentration of the acid containing acid radical ion a is greater than that of the mother liquor. The hydrogen ion concentration of the solution B obtained by the adjustment may be 5 to 10mol/L (that is, the acid concentration is 5 to 10 mol/L). And treating the rare earth raw material by using the solution B as a stripping solution. Thus, the mother liquor containing acid radical ions A can be recycled, and the fluorine-containing waste acid can be more fully utilized.
The rare earth raw material comprises a plurality of substances, and the rare earth metal solution is obtained through the extraction separation process. In the process of extracting and separating rare earth, an aqueous solution containing a plurality of rare earth metal ions is contacted with an immiscible organic solvent, one or more rare earth metal ions enter an organic phase by the action of an extracting agent, and other components are still remained in an aqueous phase, thereby achieving the purpose of separation. The extractant includes three types: acidic extractants, such as P507 or P204 (acidic phosphorus type lipids); neutral extractants such as TBP (tributyl phosphate); ion-associated extractants, such as amines. In the present invention, P507 (ethylhexyl phosphoric acid mono-2-ethyl hexyl ester) can be used in the rare earth extraction separation process.
The invention uses the solution B as the stripping solution to treat the rare earth raw material. And adding the solution B into a rare earth extraction liquid containing an extracting agent for back extraction, thereby back extracting rare earth ions from the extraction liquid into the solution B to obtain a rare earth metal salt aqueous solution. The obtained rare earth metal salt aqueous solution can be used as a raw material to react with fluorine-containing waste acid to obtain rare earth fluoride particles. The rare earth metal salt aqueous solution obtained in the step (3) and the rare earth metal salt aqueous solution obtained in the step (1) may have the same kind of rare earth ions. For example, if the aqueous rare earth metal salt solution obtained in step (1) is an aqueous lanthanum chloride solution, the aqueous rare earth metal salt solution obtained in step (3) is preferably an aqueous lanthanum chloride solution. As another example, if the aqueous rare earth metal salt solution obtained in step (1) is an aqueous lanthanum cerium chloride solution, the aqueous rare earth metal salt solution obtained in step (3) is preferably an aqueous lanthanum cerium chloride solution.
According to one embodiment of the present invention, the method for preparing rare earth fluoride particles using waste acid containing fluorine according to the present invention comprises the steps of:
dropwise adding the fluorine-containing waste acid and the lanthanum chloride aqueous solution into a base solution containing an induced crystallization agent in a parallel flow manner at 40-90 ℃, and controlling the relative dropwise adding speed of the fluorine-containing waste acid and the lanthanum chloride aqueous solution in the parallel flow dropwise adding process to obtain a reaction solution; wherein, with F - Calculated waste acid containing fluorine and RE 3+ The molar ratio of the rare earth metal salt in the lanthanum chloride aqueous solution is 2.55-2.997; controlling the relative dropping speed of the two components to F - Calculated fluorine-containing waste acid as RE 3+ The molar ratio of lanthanum chloride in the lanthanum chloride aqueous solution is 2-3.5;
solid-liquid separation is carried out on the reaction liquid to obtain rare earth fluoride precipitate and mother liquor containing chloride ions, and then the rare earth fluoride precipitate is dried and roasted to obtain rare earth fluoride particles;
and (3) regulating the hydrogen ion concentration of the hydrochloric acid mother liquor by using concentrated hydrochloric acid to obtain a solution B with the hydrogen ion concentration of 5-10 mol/L, and treating the rare earth raw material by using the solution B as a stripping solution to form a lanthanum chloride aqueous solution.
In addition, the obtained lanthanum chloride aqueous solution is continuously reacted with fluorine-containing waste acid.
In the following examples and comparative examples, the "fluorine concentration" is defined as F - And (4) calculating the molar concentration of the fluorine-containing waste acid.
Example 1
The fluorine-containing waste acid used in the embodiment is tail gas acid containing hydrofluoric acid and fluosilicic acid, which is obtained by spraying and absorbing tail gas containing hydrogen fluoride and silicon fluoride in the sulfuric acid smelting process of fluorine-containing rare earth minerals, wherein the fluorine concentration is 4mol/L.
At 40 ℃, 100ml of lanthanum chloride aqueous solution (REO, 200 g/L) and 92ml of fluorine-containing waste acid are dripped into 50ml of deionized water (base solution) containing 0.01g of oxalic acid in a cocurrent flow mode, and reaction liquid is obtained after complete reaction. The dripping speed of the lanthanum chloride aqueous solution and the fluorine-containing waste acid is respectively 1.8ml/min and 1.1ml/min.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain a lanthanum fluoride precipitate and a mother liquor (namely a hydrochloric acid-containing mother liquor) containing chloride ions A. The concentration of hydrogen ions in the mother liquor was 2.0mol/L. And drying and roasting the lanthanum fluoride precipitate to obtain lanthanum fluoride particles. Fluorine conversion of 99.7%, d of lanthanum fluoride particles 50 ＝10.2μm。
And (3) regulating the hydrochloric acid-containing mother liquor to 5mol/L of hydrogen ion concentration by using concentrated hydrochloric acid to obtain a solution B, and treating the rare earth raw material by using the solution B as a stripping solution to form a lanthanum chloride aqueous solution.
Example 2
The fluorine-containing waste acid used in the embodiment is tail gas acid containing hydrofluoric acid and fluosilicic acid, which is obtained by spraying and absorbing tail gas containing hydrogen fluoride and silicon fluoride in the sulfuric acid smelting process of fluorine-containing rare earth minerals, wherein the fluorine concentration is 5.5mol/L.
150ml of cerium chloride aqueous solution (REO, 252 g/L) and 119ml of fluorine-containing waste acid are dripped into 50ml of deionized water (base solution) containing 0.58g of ammonium oxalate at 50 ℃ in a concurrent flow manner, and reaction liquid is obtained after complete reaction. The dropping speed of the cerium chloride aqueous solution and the fluorine-containing waste acid is 1.9ml/min and 1.2ml/min respectively.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain cerium fluoride precipitate and mother liquor (namely mother liquor containing hydrochloric acid) containing chloride ions A. The concentration of hydrogen ions in the mother liquor is 2.2mol/L. And drying and roasting the cerium fluoride precipitate to obtain cerium fluoride particles. Fluorine conversion of 99.7%, d of cerium fluoride particles 50 ＝12.7μm。
And regulating the hydrochloric acid-containing mother liquor to 5mol/L of hydrogen ion concentration by using concentrated hydrochloric acid to obtain a solution B. And treating the rare earth raw material by using the solution B as a stripping solution to form a cerium chloride aqueous solution.
Example 3
The waste acid containing fluorine used in the embodiment is tail gas acid containing hydrofluoric acid and fluosilicic acid, which is obtained by spraying and absorbing tail gas containing hydrogen fluoride and silicon fluoride in a sulfuric acid smelting process of rare earth minerals containing fluorine, wherein the concentration of fluorine is 6mol/L.
200ml of lanthanum cerium chloride aqueous solution (REO, 283 g/L) and 184ml of fluorine-containing waste acid are dripped into 50ml of deionized water (base solution) containing 2.36g of ammonium oxalate in a concurrent flow manner at the temperature of 55 ℃, and reaction liquid is obtained after complete reaction. The dripping speed of the lanthanum cerium chloride aqueous solution and the fluorine-containing waste acid is respectively 2.0ml/min and 1.7ml/min.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain a lanthanum cerium fluoride precipitate and a mother liquor (namely a hydrochloric acid-containing mother liquor) containing chloride ions A. The concentration of hydrogen ions in the mother liquor was 3.3mol/L. And drying and roasting the lanthanum fluoride cerium precipitate to obtain lanthanum fluoride cerium particles. Fluorine conversion of 99.8%, d of lanthanum cerium fluoride particles 50 ＝13.1μm。
And regulating the hydrochloric acid-containing mother liquor to the hydrogen ion concentration of 8mol/L by using concentrated hydrochloric acid to obtain a solution B. And treating the rare earth raw material by using the solution B as a stripping solution to form a lanthanum cerium chloride aqueous solution.
Example 4
The waste acid containing fluorine used in the embodiment is tail gas acid containing hydrofluoric acid and fluosilicic acid, which is obtained by spraying and absorbing tail gas containing hydrogen fluoride and silicon fluoride in a sulfuric acid smelting process of rare earth minerals containing fluorine, wherein the concentration of fluorine is 9mol/L.
500ml of yttrium nitrate aqueous solution (REO, 297 g/L) and 350ml of fluorine-containing waste acid were added dropwise in parallel to 100ml of deionized water (base solution) containing 11.8g of oxalic acid at 65 ℃ to obtain a reaction solution after completion of the reaction. The dropping speed of the yttrium nitrate aqueous solution and the fluorine-containing waste acid is respectively 10.0ml/min and 7.5ml/min.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain yttrium fluoride precipitate and mother liquor containing nitrate ions A (namely the mother liquor containing nitric acid). The concentration of hydrogen ions in the mother liquor was 4.4mol/L. And drying and roasting the yttrium fluoride precipitate to obtain yttrium fluoride particles. Fluorine conversion of 99.9%, d of Yttrium fluoride particles 50 ＝17.8μm。
And regulating the nitric acid-containing mother liquor to the hydrogen ion concentration of 8mol/L by using concentrated nitric acid to obtain a solution B. And treating the yttrium ion-containing raw material by using the solution B as a stripping solution to form an yttrium nitrate aqueous solution.
Example 5
The waste acid containing fluorine used in the embodiment is tail gas acid containing hydrofluoric acid and fluosilicic acid, which is obtained by spraying and absorbing tail gas containing hydrogen fluoride and silicon fluoride in a sulfuric acid smelting process of rare earth minerals containing fluorine, wherein the concentration of fluorine is 15mol/L.
300ml of neodymium nitrate aqueous solution (REO, 264 g/L) and 91ml of fluorine-containing waste acid are dripped into 50ml of deionized water (base solution) containing 14.56g of neodymium oxalate in a concurrent flow manner at the temperature of 45 ℃, and reaction liquid is obtained after complete reaction. The dropping speed of the neodymium nitrate aqueous solution and the fluorine-containing waste acid is respectively 2.5ml/min and 0.9ml/min.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain a neodymium fluoride precipitate and a mother liquid containing nitrate ions A (namely the mother liquid containing nitric acid). The concentration of hydrogen ions in the mother liquor was 3.4mol/L. And drying and roasting the neodymium fluoride precipitate to obtain neodymium fluoride particles. Fluorine conversion of 99.8%, d of Neodymium fluoride particles 50 ＝16.3μm。
And regulating the nitric acid-containing mother liquor to the hydrogen ion concentration of 10mol/L by using concentrated nitric acid to obtain a solution B. And treating the rare earth raw material by using the solution B as a stripping solution to form a neodymium nitrate aqueous solution.
Comparative example 1
This comparative example differs from example 1 mainly in that the cocurrent dropwise addition mode is not employed. The aqueous solution of rare earth metal salt is added into the base solution, and then the fluorine-containing waste acid (tail gas acid) is added. The details are as follows:
at 40 ℃, 100ml of lanthanum chloride aqueous solution (REO, 200 g/L) is dripped into 50ml of deionized water (base solution) containing 0.01g of oxalic acid, then 92ml of tail gas acid is dripped, and reaction liquid is obtained after complete reaction. The dripping speed of the lanthanum chloride water solution and the tail gas acid is respectively 1.8ml/min and 1.1ml/min.
And (3) carrying out solid-liquid separation on the reaction liquid to obtain lanthanum fluoride precipitate and hydrochloric acid mother liquor. The concentration of hydrochloric acid in the mother liquor is 1.9mol/L. Drying and roasting the precipitate to obtain the lanthanum fluoride particles. Fluorine conversion was 89.9%, d of lanthanum fluoride particles 50 ＝2.3μm。
TABLE 1
Note: m represents by F - Calculated waste acid containing fluorine and RE 3+ The molar ratio of the rare earth metal salt in the rare earth metal salt aqueous solution is calculated; n represents during the cocurrent dropwise addition, as F - Calculated fluorine-containing waste acid and RE 3+ The molar ratio of the rare earth metal salt in the aqueous solution of the rare earth metal salt.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (5)
1. A method for preparing rare earth fluoride particles by using fluorine-containing waste acid is characterized by comprising the following steps:
(1) Dripping the fluorine-containing waste acid and the rare earth metal salt aqueous solution into the base solution in a parallel flow manner for reaction to obtain a reaction solution; wherein the rare earth metal salt contains acid radical ion A; the fluorine-containing waste acid contains fluorine ions; the base solution is water or an acidic aqueous solution; the fluorine-containing waste acid and/or the base solution contains carboxylic acid or salt thereof capable of releasing free carboxylate radicals as a crystallization-inducing agent;
(2) Solid-liquid separation is carried out on the reaction liquid to obtain rare earth fluoride precipitate and mother liquor containing acid radical ions A; drying and roasting the rare earth fluoride precipitate to obtain rare earth fluoride particles; and
(3) Adjusting the hydrogen ion concentration of the mother solution containing the acid radical ions A by adopting acid containing the acid radical ions A to obtain solution B, and treating the rare earth raw material by using the solution B as stripping solution to form the rare earth metal salt aqueous solution;
wherein the rare earth metal salt in the rare earth metal salt aqueous solution is selected from one of rare earth chloride and rare earth nitrate;
wherein the molar weight of the induced crystallization agent calculated by carboxylate radical is X, and the rare earth metal salt in the rare earth metal salt aqueous solution is RE 3+ Calculating the molar quantity of the needed carboxylate radical as Y according to the molecular stoichiometric ratio on the basis, and then the dosage of the induced crystallization agent conforms to the following formula:
X/Y＝0.5～10％；
wherein the induced crystallization agent is selected from one or more of ammonium oxalate, sodium oxalate, rare earth oxalate, ammonium malonate, sodium malonate, ammonium propionate and sodium propionate;
wherein the fluorine-containing waste acid is waste acid containing fluorine silicic acid, or waste acid containing hydrofluoric acid and fluosilicic acid;
wherein, with F - Calculated waste acid containing fluorine and RE 3+ The molar ratio of the rare earth metal salt in the rare earth metal salt aqueous solution is 2.56-2.995.
2. The method according to claim 1, wherein the fluorine-containing waste acid is (1) fluosilicic acid formed in phosphate fertilizer production, or (2) tail gas acid containing hydrofluoric acid and fluosilicic acid generated in a fluorine-containing rare earth mineral sulfuric acid smelting process.
3. The process of claim 1, wherein the relative drop rates of the aqueous solution of spent fluoride acid and rare earth metal salt are controlled such that the drop is F during co-current dropping - Calculated fluorine-containing waste acid and RE 3+ The molar ratio of the rare earth metal salt in the rare earth metal salt aqueous solution is 2-3.5.
4. The method of claim 1, wherein the cocurrent dropwise addition is carried out at a temperature of 40 to 90 ℃.
5. The method according to any one of claims 1 to 4, wherein the hydrogen ion concentration of the solution B is 5 to 10mol/L.
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