A method for continuously preparing large-particle rare earth fluorocarbon acid and co-producing nanometer spherical silicon dioxide by using fluorosilicon mixed waste acid

Abstract

The application discloses a method for continuously preparing large-particle rare earth fluorocarbonate and co-producing nanometer spherical silicon dioxide by using fluorosilicon mixed waste acid, and belongs to the technical field of rare earths. Silicon is removed from the fluorosilicon mixed waste acid to obtain an alkaline fluorine-containing solution and silicon dioxide, the alkaline fluorine-containing solution is mixed with a monobasic alkaline mixed solution to obtain a composite precipitation solution A, and the composite precipitation solution A is subjected to a continuous precipitation reaction with a soluble rare earth salt solution B to obtain rare earth fluorocarbonate. The continuous precipitation reaction comprises induction nucleation, dielectric growth, control of an end point and ripening of a crystal form, realizes accurate control of each stage of nucleation, growth and crystallization of the rare earth fluorocarbonate, and has the advantages of obvious perfect precipitation crystal form, large particle size and uniform fluorination. The co-produced SiO2 has a spherical single crystal shape, high purity and wide application fields. The application combines the treatment of fluorosilicon mixed waste acid produced in the fields of rare earths and phosphorus chemical industry with the development of rare earth fluoride functional materials, and provides an industrial feasible technical scheme for high-value utilization of fluorine / silicon resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rare earth, in particular to a method for continuously preparing large-particle fluorocarbon acid rare earth and co-producing nanometer spherical silicon dioxide by using fluorosilicon mixed waste acid. BACKGROUND

[0002] There are two traditional production methods for fluorocarbon acid rare earth, one is fluorination followed by carbon deposition, that is, a fluorination agent is first reacted with part of the rare earth solution, and then completely precipitated with a carbonate; the other is carbon deposition followed by fluorination, that is, the rare earth solution is first completely precipitated with a carbonate, and then partially fluorinated with a fluorination agent after washing. No matter which process is two-step reaction, there are problems such as long process time, uneven reaction, local fluorination, amorphous precipitation, more impurities entrained, and low fluorination efficiency. At the same time, fluorocarbon acid rare earth is widely used as a precursor of fluorine-containing rare earth polishing powder material, and the fluorocarbon acid rare earth synthesized by the traditional preparation method leads to lattice defects, uneven size of agglomerates, and low polishing precision and rate in the downstream polishing powder.

[0003] The patent with publication number CN110885637B discloses a preparation method of fluorinated rare earth polishing powder and fluorinated rare earth polishing liquid, which uses a high-energy ball mill to fully mix the rare earth carbonate and the fluorinated rare earth, and adds additives, spray drying and other processing methods to prepare the fluorinated rare earth polishing powder, so that the precursor is uniformly mixed, and high cutting rate is achieved under the premise of ensuring that the surface of the optical glass has no scratches and other surface defects. However, the ball milling process belongs to mechanical force chemical effect, and the crystal lattice structure is not completely uniform, resulting in free state fluoride ions and fluorides causing polishing scratch defects. In addition, a small amount of fluorinated rare earth is hydrolyzed to release fluoride ions during the ball milling process, so that HF acid gas is generated by direct evaporation of fluorine-containing wastewater during the spray drying process, which corrodes the equipment, and the equipment is seriously aged for a long time.

[0004] The patent with publication number CN112724839B discloses a system and method for preparing rare earth polishing powder, which uses a wet ball milling device, a dehydration drying device and a modification device to prepare fluorinated carbonic acid rare earth, realizes the refinement of carbonic acid rare earth before modification, and makes the crystal size of the carbonic acid rare earth precursor uniform and the fluorination reaction complete. However, the particle size and morphology are completely controlled by the carbonic acid rare earth, the process is complicated, the carbonic acid rare earth needs to go through stirring, sand milling, ball milling and modification process, which is time-consuming and low in efficiency.

[0005] The patent application of patent publication number CN104387988B discloses a preparation method of superfine fluorine-containing cerium-based polishing powder. The superfine fluorine-containing cerium-based polishing powder is prepared by co-precipitation of a mixed solution of a rare earth salt solution, a carbonate precipitant and a fluorination agent. The application has the advantages of low reaction temperature and short reaction and aging time, but the precursor particle size is small, which causes filtration difficulty, and the raw material concentration is low, only 100-150 g / L, and the production per unit time is low. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a method for continuously preparing large particle fluorocarbon acid rare earth and co-producing nanometer spherical silica using fluorine-silicon mixed waste acid. The present application first stirs and mixes fluorine-silicon mixed waste acid with ammonia solution, then compounding the alkaline fluorine-containing solution with the monobasic alkaline mixed solution to obtain composite precipitation solution A, and finally continuously adding composite precipitation solution A and soluble rare earth salt solution B into the continuous precipitation reaction device for reaction, and obtaining large particle fluorocarbon acid rare earth after solid-liquid separation. The continuous precipitation reaction of the present application includes four units: nucleation induction unit, dielectric growth unit, end point control unit and crystallization unit, which realizes accurate control of each stage of fluorocarbon acid rare earth from nucleation, growth to crystallization, has obvious advantages of perfect precipitation crystal form, large particle, uniform fluorination, etc. At the same time, the co-produced SiO2 single crystal has spherical shape, high purity and wide application field. The present application further combines the treatment of fluorine-silicon mixed waste acid produced in the rare earth and phosphorus chemical industry with the development of rare earth fluoride functional materials, and provides an industrial feasible technical solution for high-value utilization of fluorine / silicon resources.

[0007] The present application achieves the above-mentioned purposes through the following technical solutions.

[0008] The present application provides a method for continuously preparing large particle fluorocarbon acid rare earth and co-producing nanometer spherical silica using fluorine-silicon mixed waste acid, which includes the following steps:

[0009] (1) Silicon removal from fluorine-silicon mixed waste acid: stir and mix fluorine-silicon mixed waste acid with ammonia water to obtain alkaline fluorine-containing solution and nanometer spherical silica;

[0010] (2) Compound precipitant: compound the alkaline fluorine-containing solution obtained in step (1) with a monobasic alkaline mixed solution to obtain composite precipitation solution A;

[0011] (3) Continuous and flow precipitation: continuously precipitate the composite precipitation solution A obtained in step (2) with soluble rare earth salt solution B;

[0012] (4) Solid-liquid separation: filter the aged slurry obtained in step (3) to obtain filter cake and filtrate, the filtrate is ammonium salt aqueous solution or sodium salt aqueous solution, and the filter cake is large particle fluorocarbon acid rare earth;

[0013] The particle size D of the large particle fluorocarbon acid rare earth is 28-1000 μm, and the particle size range is (D 50 ≥28 μm, the particle size range is (D 90 -D 10 ) / D 50 ≤1.5; the primary particle size D of the nanospherical silicon dioxide is ≤300 nm, and the particle size range is (D 50 ≤300 nm, the particle size range is (D 90 -D 10 ) / D 50 ≤1.5;

[0014] In step (3), the continuous precipitation reaction comprises in sequence the processes of inducing nucleation, dielectric growth, controlling end point and ripening crystallization.

[0015] Preferably, in step (1), the fluorosilicon mixed waste acid is selected from waste acid containing fluorosilicon acid or waste acid containing hydrofluoric acid and fluorosilicon acid, the content of fluorine element in the fluorosilicon mixed waste acid is 90-250 g / L, and the content of silicon element is 0.5-10 wt%; the pH value of the alkaline fluorine-containing solution obtained by stirring and mixing the fluorosilicon mixed waste acid with ammonia water is controlled to be 7.2-9.5.

[0016] Preferably, in step (2), the monobasic alkaline mixed solution is selected from a mixed solution of carbonate and lye, the carbonate is selected from at least one of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate and sodium carbonate liquid or solid, and the lye is selected from at least one of ammonia water and sodium hydroxide solution; the molar ratio of the alkaline fluorine-containing solution calculated in terms of F - to the monobasic alkaline mixed solution calculated in terms of HCO3 - is (0.267-1):1.

[0017] Preferably, in step (3), the soluble rare earth salt solution is selected from one of rare earth chloride, rare earth sulfate, rare earth nitrate and rare earth acetate, and the temperature of the whole process of the continuous precipitation reaction is 25-80℃.

[0018] Preferably, in step (3), the continuous precipitation reaction is carried out in a continuous precipitation reaction device, the composite precipitation solution A and the soluble rare earth salt solution B are continuously added into the continuous precipitation reaction device, the continuous precipitation reaction device is sequentially divided into four units of inducing nucleation unit, dielectric growth unit, controlling end point unit and ripening crystalline form unit, and the processes of inducing nucleation, dielectric growth, controlling end point and ripening crystallization are respectively carried out, the feeding mode of each unit is from the bottom of the reaction device, and the reaction time of each unit is ≥30 min.

[0019] The continuous precipitation reaction device is divided into 7 stages, the reaction slurry of each stage is self-escaped to the next stage, but the slurry does not flow into the next stage completely, and the bottom liquid is left at the bottom, and the raw materials continuously flow into the bottom liquid of the previous round in the device.

[0020] Preferably, the nucleation-inducing unit is arranged as a first-stage reaction device, and the composite precipitation solution A and the soluble rare earth salt solution B are added into the first-stage reaction device in parallel flow to carry out the rare earth fluoride nucleation-inducing reaction, and the obtained first-stage crystal seed slurry is automatically overflowed into the next-stage reaction device.

[0021] The dielectric growth unit is arranged as a second-stage to fourth-stage reaction device, and the composite precipitation solution A is added into the second-stage to fourth-stage reaction device to carry out the rare earth fluoride crystal nucleation dielectric growth reaction, and the obtained growth slurry is automatically overflowed into the next-stage reaction device.

[0022] The end-point control unit is arranged as a fifth-stage to sixth-stage reaction device, and is provided with an on-line pH detector, and the monobasic alkaline mixed solution and / or the first-stage crystal seed slurry is added into the fifth-stage to sixth-stage reaction device to carry out the complete precipitation reaction of rare earth, and the obtained complete precipitation slurry is automatically overflowed into the next-stage reaction device.

[0023] The ripening crystal unit is arranged as a seventh-stage reaction device, and the overflow slurry of the previous stage is subjected to ripening reaction to obtain the ripened rare earth fluoride slurry.

[0024] Preferably, in the first-stage reaction device, the relative drop molar ratio of the composite precipitation solution A calculated based on anion (F - +HCO3 - ) to the soluble rare earth salt solution B calculated based on cation RE 3+ ) is (0.23-2.56):1; in the second-stage to fourth-stage reaction device, the total molar ratio of the composite precipitation solution A calculated based on anion (F - +HCO3 - ) to the soluble rare earth salt solution B calculated based on total cation RE 3+ ) is (0.44-2.77):1.

[0025] Preferably, the end point of the complete precipitation reaction is controlled at a pH value of 6.2-8.0.

[0026] The application also provides a large-particle rare earth fluocarbonate and nanometer spherical silica prepared by the above-mentioned method.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] (1) The application avoids the problems of the traditional liquid-phase preparation of rare earth fluocarbonate, such as the controlled fluorination of the fluorinated crystal form, the non-uniform fluorination, the low fluorination rate caused by physical and mechanical methods, and the existence of free fluorine, and adopts the liquid-phase continuous parallel-flow precipitation technology to divide the whole precipitation process into four units according to the reaction mechanism, i.e., nucleation-inducing unit, dielectric growth unit, complete precipitation unit and ripening crystal unit, and further controls the process kinetics to realize the perfect crystal form, large particle and high fluorination efficiency of the rare earth fluocarbonate.

[0029] (2) The present application avoids the problem of inheriting impurities in fluorocarbonic acid rare earth from the front-end product caused by the traditional two-step synthesis method. According to the solubility product difference between high-valence rare earth and low-valence conventional impurity fluoride under acidic conditions, the process pH value is controlled through parallel flow mode, so that the impurities can be removed synchronously, and high-quality fluorocarbonic acid rare earth is obtained.

[0030] (3) The present application adopts a complex precipitant containing F - , HCO3 - and OH - for liquid phase reaction. The introduction of OH - can enhance the concentration of liquid alkali of the precipitant, improve the reaction efficiency, replace part of HCO3 - with OH - , reduce CO2 emission, equivalent to reducing energy consumption, and reduce the cost of wet processing.

[0031] (4) The present application is suitable for high-value utilization of fluorosilicon mixed waste acid generated in rare earth and phosphorus chemical industry. The process has the advantages of saving raw material cost, fluorosilicon wastewater treatment cost, greatly improving the production yield of continuous production, and stable product quality, and the economic and social benefits are very significant. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 is the process flow diagram of Example 1;

[0034] Figure 2 is the schematic diagram of the continuous precipitation reaction process of Example 1;

[0035] Figure 3 In the figure, (a) is the electron microscope graph of SiO2 solid prepared in step (1) of Example 1, and (b) is the electron microscope graph of lanthanum cerium fluorocarbonate prepared in step (4) of Example 1. DETAILED DESCRIPTION

[0036] Now, various exemplary embodiments of the present application will be described in detail. The detailed description should not be considered as limiting the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application. It should be understood that the terms described in the present application are only for describing the particular embodiments, and are not used to limit the present application.

[0037] In addition, for numerical ranges recited herein, it is contemplated that every number within that range and each smaller range between the recited upper and lower limits is also specifically contemplated. For example, it is contemplated that every number within a recited range and every smaller range between the recited upper and lower limits is specifically contemplated. The upper and lower limits of these smaller ranges can independently be included or excluded in the ranges.

[0038] 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 application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials that are related to the present application. In the case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification controls.

[0039] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0040] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", and the like are open-ended terms that are intended to permit but not limit the inclusion of elements or the number of elements, as well as the possibility that one or more other elements can be added or otherwise included.

[0041] In the following examples, room temperature means 25-35°C, "D 10 " is the cumulative value of a sample, which means the particle size value corresponding to the cumulative distribution percentage of 10% in the particle size distribution from small to large. Its physical meaning is that the particles with a particle size smaller than it account for 10%. 50 " is the median diameter or median particle size, which means the particle size corresponding to the cumulative distribution percentage of 50% of a sample. Its physical meaning is that the particles with a particle size larger than it account for 50%, and the particles with a particle size smaller than it also account for 50%. 90 " is the cumulative value of a sample, which means the particle size value corresponding to the cumulative distribution percentage of 90% in the particle size distribution from small to large. Its physical meaning is that the particles with a particle size smaller than it account for 90%.

[0042] In the present application, the conversion rate of fluorine = (the number of moles of fluorocarbon rare earth carbonate in terms of F - ÷ the number of moles of fluorosilicon mixed acid in terms of F - ) x 100%.

[0043] The method of the present application comprises the following steps: (1) a silicon removal step; (2) a complexing precipitant preparation step; (3) a continuous and parallel flow precipitation step; and (4) a solid-liquid separation step. The details are described as follows.

[0044] Silicon removal step

[0045] The fluorosilicon mixed waste acid is added dropwise into the ammonia solution, the reaction solution is stirred, and the terminal pH value of the solution is controlled to be 7.2-9.5, preferably 7.5-9.3, and more preferably 7.8-9.0. The reaction solution is subjected to solid-liquid separation to obtain a basic fluorine-containing solution and nanometer spherical silicon dioxide. In the present application, the fluorosilicon mixed waste acid is added dropwise into the ammonia solution in a reverse hydrolysis mode, the intermediate product SiF6 2- The condensation reaction is prone to occur under strong alkaline conditions, the hydrolysis rate is slowed down, and the generated nanometer SiO2 crystal grains are spherical and nucleated uniformly.

[0046] In the present application, the fluorosilicon mixed waste acid can be selected from waste acid containing fluorosilicic acid or waste acid containing hydrofluoric acid and fluorosilicic acid. Preferably, the fluorosilicon mixed waste acid is selected from mixed acid containing hydrofluoric acid and fluorosilicic acid. More preferably, the fluorosilicon mixed waste acid is selected from mixed acid containing hydrofluoric acid and fluorosilicic acid with a fluorosilicon mass ratio of 1:0.08-0.20.

[0047] Complex precipitant preparation step

[0048] The basic fluorine-containing solution is mixed with a monobasic alkaline mixed solution to obtain a complex precipitation solution A.

[0049] In the present application, the monobasic alkaline mixed solution can be selected from a mixed solution of carbonate and lye, the carbonate being selected from at least one of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate liquid or solid, and the lye being selected from at least one of ammonia water and sodium hydroxide liquid. The molar ratio of the carbonate to the lye can be selected from (5.67-0.82):1, preferably (4.0-1.0):1, and more preferably (2.33-1.50):1. Compared with the traditional single carbonate precipitant, the present application introduces OH - The liquid alkali concentration of the precipitant can be enhanced, and the reaction efficiency can be improved; at the same time, OH - Part of HCO3 - is replaced, CO2 emission is reduced, since heat energy is taken away during the CO2 emission process, reducing CO2 emission is equivalent to reducing energy consumption, reducing the cost of wet processing, and realizing the environmental protection significance of energy saving and carbon reduction.

[0050] In the present application, the basic fluorine-containing solution is F - , and the monobasic alkaline mixed solution is HCO3 -The molar ratio of the alkaline mixed solution of the composite precipitation solution A and the soluble rare earth salt solution B can be selected from (0.267-1):1, preferably (0.355-0.800):1, and more preferably (0.373-0.711):1. Controlling the fluorine quality in this range is beneficial to the stability of fluorine in the downstream roasting process and avoids the volatilization of fluorine-containing gas.

[0051] Continuous and co-current precipitation step

[0052] The composite precipitation solution A and the soluble rare earth salt solution B are continuously added into a continuous precipitation reaction device for reaction. The whole continuous precipitation process is divided into four units, i.e., a nucleation induction unit, a dielectric growth unit, a terminal control unit and a crystal type ripening unit. Each unit is fed from the bottom of the reaction device and is precisely controlled by different control conditions. The temperature of the whole continuous precipitation process in the present application can be selected from room temperature to 80°C, preferably 30-78°C, and more preferably 45-75°C. Controlling the temperature in this range is beneficial to increasing the critical radius of grain nucleation and improving the generation speed of the crystal grains, so as to make the crystal grains grow. However, the temperature should not be too high, because the carbonate is easy to decompose under heat, which causes the molecular kinetic energy in the system to be too large, resulting in unstable crystallization process. The reaction time of each unit can be selected to be ≥30 min, preferably ≥40 min, and more preferably ≥45 min.

[0053] The soluble rare earth salt solution in the present application is an aqueous solution containing a soluble rare earth salt. The soluble rare earth salt is selected from one of rare earth chloride, rare earth sulfate, rare earth nitrate and rare earth acetate. The rare earth metal in the soluble rare earth salt can be selected from one or more of lanthanum, cerium, praseodymium, neodymium and samarium. Of course, the rare earth metal in the soluble rare earth salt can not be limited to these, as long as it can form an aqueous solution.

[0054] The nucleation induction unit is provided with a first-stage reaction device. The composite precipitation solution A and the soluble rare earth salt solution B are co-currently added into the first-stage reaction device for fluorocarbon rare earth nucleation induction reaction, and the obtained crystal nucleus slurry is automatically overflowed into the next-stage reaction device. In the first-stage reaction device of the present application, the composite precipitation solution A is calculated as anion (F - +HCO3 - ) and the soluble rare earth salt solution B is calculated as cation RE 3+The relative dropwise molar ratio of the soluble rare earth salt solution B calculated as the solubility of the rare earth salt can be selected from (0.23-2.56):1, preferably (0.30-2.25):1, and more preferably (0.33-2.07):1. It should be noted that, according to the solubility product of the fluorinated rare earth being much smaller than that of the rare earth carbonate, and the concurrent dropwise addition process, part of the rare earth carbonate crystal nucleus is replaced by fluorine to induce the formation of fluorocarbonic acid rare earth crystal nucleus, thereby avoiding the formation of amorphous crystal nucleus of the fluorinated rare earth. At the same time, the instantaneous concentration of the concurrent dropwise addition of the rare earth salt solution and the composite precipitation solution is used to control the nucleation of the particles. Since the instantaneous concentration is low, the ion collision probability in the crystallization process is reduced, the nucleation growth time is prolonged, thereby promoting the growth of the crystal nucleus, and the lower reaction concentration greatly reduces the pH fluctuation in the reaction process, thereby providing a stable nucleation environment.

[0055] The dielectric growth unit is provided as a 2-4 stage reaction device, the composite precipitation solution A is added to the 2-4 stage reaction device for the dielectric growth reaction of the fluorocarbonic acid rare earth crystal nucleus, and the obtained growth slurry is automatically overflowed to the next stage reaction device. In the present application, the total composite precipitation solution A added in the 2-4 stage reaction is calculated as the anion (F - +HCO3 - ) and accounts for 0.44-2.77:1 of the total cation RE 3+ The molar ratio of the soluble rare earth salt solution B calculated as the total cation RE - It should be noted that the ammonium salt or sodium salt reaction system causes the Zeta potential of the fluorocarbonic acid rare earth particles to increase, and the ammonium cation or sodium cation is extruded into the adsorption layer, thereby reducing the repulsive potential barrier of the crystal grain. At the same time, OH

[0056] The control end unit is provided as a 5-6 stage reaction device, which is provided with an online pH detector, a monobasic alkaline mixed solution and / or a 1st stage crystal seed slurry. The monobasic alkaline mixed solution and / or the 1st stage crystal seed slurry are added to the 5-6 stage reaction device for the complete precipitation reaction of the rare earth, and the obtained complete precipitation slurry is automatically overflowed to the next stage reaction device. In the present application, the complete precipitation reaction end point pH value can be selected from 6.2-8.0, preferably 6.3-7.5, and more preferably 6.4-7.2. The monobasic alkaline mixed solution is used to control the reaction end point to ensure the complete precipitation of the rare earth resources, so that even a small amount of rare earth hydroxide can be used for the rare earth polishing powder material, and the waste water does not contain F element. It should be further noted that, the 1st stage crystal seed slurry is added to the 5th stage reaction device, so that the particle crystallization process is carried out at a lower supersaturation, thereby further ensuring the growth of the crystal.

[0057] The ripening crystal form unit is configured as a 7-stage reaction device. The overflow slurry from the previous stage undergoes a ripening reaction to obtain a rare earth fluorocarbonate ripening slurry. It should be noted that the agitator type of the ripening crystal form unit is different from that of the previous unit. Rake-type, anchor-type, and other agitators can be selected. The shear force generated is moderate, which can uniformly disperse solid particles in the liquid and keep them in suspension, which is conducive to the ripening and fine growth of particles.

[0058] Solid-liquid separation steps

[0059] The aging slurry undergoes solid-liquid separation, which includes filtering the slurry to obtain a filter cake and a filtrate. The filtrate is an aqueous solution of ammonium salt or sodium salt, and the filter cake is composed of large-particle rare earth fluorocarbonate. In this invention, since the large-particle rare earth fluorocarbonate slurry is easily filtered, the filtration method is not particularly limited. For example, a vacuum filter can be used to obtain the filter cake and filtrate. The filter cake is then rinsed or washed to directly obtain the large-particle rare earth fluorocarbonate.

[0060] Example 1

[0061] A method for the continuous preparation of large-particle rare earth fluorocarbonate and the co-production of nano-spherical silica using mixed fluorosilicone waste acid comprises the following steps:

[0062] (1) Removal of silicon from mixed fluorosilicone waste acid: At room temperature, mixed fluorosilicone waste acid (F: 92.24 g / L, Si: 7.81 wt%) was added dropwise to an analytical grade 28% ammonia solution and stirred until the pH of the solution reached 9.0. The solution was then filtered using a vacuum filtration pump to obtain an alkaline fluorine-containing solution (F: 75.46 g / L, SiO2 < 0.01 g / L). The filter cake was solid SiO2 (particle size D). 50 =194.6nm, (D 90 -D 10 ) / D 50 =1.3).

[0063] (2) Compound 3M compound precipitation solution (nF - :nHCO3 - =0.3, nNH4HCO3:nNH4OH=6:4): Under stirring at room temperature, measure 1.5L of alkaline fluoride solution and 7.1L of alkaline mixed solution (1.57Kg of ammonium bicarbonate and 995mL of 28wt% ammonia water dissolved in deionized water and diluted to 7.1L) to form a composite precipitate solution.

[0064] (3) Continuous co-current liquid-phase precipitation reaction: The reaction temperature for stages 1-7 is controlled at 60℃, using lanthanum chloride and cerium chloride solution ( Figure 2 (C) labeled as "Solution B") REO : 266.58 g / L) and composite precipitation solution ( Figure 2The lanthanum cerium chloride solution was fed from the bottom of the first device, with a feeding speed of 83 mL / min, the complex precipitation solution was fed at a speed of 43.7 mL / min, and the reaction slurry was overflowed to the second reaction after stirring for 1 h; the complex precipitation solution was fed from the bottom of the second to fourth devices at speeds of 43.7 mL / min, 22.0 mL / min and 22.0 mL / min respectively, and the reaction slurry was overflowed to the next reaction after stirring; the basic mixed solution and the first reaction slurry (in which the pH was adjusted to 8.7) were fed from the bottom of the fifth device at a speed of 20 mL / min, the reaction was stopped after the pH was adjusted to 6.8, and the slurry was finally overflowed to the seventh device. Figure 2 The seed crystals were fed from the bottom of the fifth to sixth devices at a speed of 20 mL / min, the reaction was stopped after the pH was adjusted to 6.8, and the slurry was finally overflowed to the seventh device; the seventh device was used for aging reaction (stirring aging), and the final aging slurry was obtained after 1 h.

[0065] (4) Solid-liquid separation: the aging slurry obtained in step (3) was filtered by vacuum filtration to obtain ammonium chloride wastewater and a filter cake, and the filter cake was repeatedly washed with water to obtain lanthanum cerium fluocarbonate (particle size D 50 = 50.51 μm, (D 90 -D 10 ) / D 50 = 1.2, and the fluorine conversion rate was 99.8%).

[0066] Figure 1 The process flow diagram of this embodiment is shown in Figure 1; Figure 2 Figure 2 is a schematic diagram of the continuous and parallel flow liquid phase precipitation reaction process in step (3) of this embodiment; Figure 3 Figures 3(a) and 3(b) are electron micrographs of the SiO2 solid prepared in step (1) and the lanthanum cerium fluocarbonate prepared in step (4), respectively. Figure 3 It can be seen that the SiO2 prepared in the present application has a nanospherical particle agglomerate morphology, and the lanthanum cerium fluocarbonate has a large particle flake agglomerate morphology.

[0067] Example 2

[0068] A method for continuously preparing large particle rare earth fluocarbonate and co-producing nanospherical silicon dioxide from fluorosilicon mixed waste acid is as follows:

[0069] (1) Removal of silicon from the fluorosilicon mixed waste acid: the fluorosilicon mixed waste acid (F: 105.2 g / L, Si: 6.44 wt%) was added dropwise to an analytical grade 28% ammonia solution under room temperature conditions, and stirred until the pH of the solution was 8.7; a basic fluorine-containing solution (F: 89.42 g / L, SiO2<0.01 g / L) was obtained by vacuum filtration with a filter pump, and the filter cake was SiO2 solid (particle size D 50 = 187.2 nm, (D 90 -D 10 ) / D 50 = 1.3).

[0070] (2) Complexing 3M precipitating solution (nF - : nHCO3 - = 0.4, nNaHCO3: nNaOH = 6:4): 1.5 L of the basic fluorine-containing solution was mixed with 6.7 L of the basic mixed solution (1.48 Kg of sodium bicarbonate and 0.47 Kg of sodium hydroxide) to form a complex precipitating solution under stirring at room temperature.

[0071] (3) Continuous and co-current liquid phase precipitation reaction: the temperature of the 1st to 7th stage was controlled at 60°C. The lanthanum cerium chloride solution (C REO : 266.58 g / L) and the complex precipitating solution were fed from the bottom of the 1st stage device. The feeding speed of the lanthanum cerium chloride solution was 83 mL / min, and the feeding speed of the complex precipitating solution was 43.7 mL / min. The reaction slurry was overflowed to the 2nd stage after stirring for 1 h. The complex precipitating solution was fed from the bottom of the 2nd to 4th stage device, and the feeding speeds were 43.7 mL / min, 26.0 mL / min and 17.5 mL / min, respectively. The reaction slurry was overflowed to the next stage after stirring. The basic mixed solution and the 1st stage reaction slurry were fed from the bottom of the 5th to 6th stage device at a speed of 20 mL / min. The feeding was stopped after the reaction slurry was stirred to pH 6.8. The slurry was finally overflowed to the 7th stage. The 7th stage slurry was subjected to ripening reaction, and the final ripening slurry was obtained after 1 h.

[0072] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain sodium chloride wastewater and a filter cake. The filter cake was repeatedly washed with water to obtain lanthanum cerium fluorocarbonate (particle size D 50 = 40.42 μm, (D 90 -D 10 ) / D 50 = 1.5, and fluorine conversion rate = 99.9%).

[0073] Example 3

[0074] The method for continuously preparing large-particle rare earth fluorocarbonate and co-producing nanometer spherical silica from fluorosilicon mixed waste acid is as follows:

[0075] (1) Removal of silicon from fluorosilicon mixed waste acid: under room temperature, the fluorosilicon mixed waste acid (F: 105.2 g / L, Si: 6.44 wt%) was added dropwise into an analytical pure 28% ammonia solution under stirring until the pH of the solution was 8.7. The basic fluorine-containing solution (F: 89.42 g / L, SiO2< 0.01 g / L) was obtained by vacuum filtration pump filtration, and the filter cake was SiO2 solid (particle size D 50 = 192.5 nm, (D 90 -D 10 ) / D 50 = 1.3).

[0076] (2) Complexing 3M precipitating solution (nF -:nHCO3 - =0.55, nNH4HCO3:nNH4OH = 7:3): Under stirring at room temperature, measure 2L of alkaline fluoride solution and 6.8L of alkaline mixed solution (1.35Kg of ammonium bicarbonate and 551mL of 28wt% ammonia water dissolved in deionized water and diluted to 6.8L) to form a composite precipitate solution.

[0077] (3) Continuous co-current liquid-phase precipitation reaction: The reaction temperature for stages 1-7 is controlled at 60℃, and the praseodymium chloride solution (C REO The praseodymium chloride (271 g / L) and the composite precipitate solution were fed from the bottom of the first-stage unit. The praseodymium chloride solution was fed at a rate of 25 mL / min, and the composite precipitate solution was fed at a rate of 10.8 mL / min. After stirring for 1 hour and 20 minutes, the reaction slurry overflowed to the second-stage reaction. The composite precipitate solution was fed from the bottom of the second- to fourth-stage units at rates of 10.8 mL / min, 8.1 mL / min, and 2.7 mL / min, respectively. After stirring, the reaction slurry overflowed to the next stage reaction. The alkaline mixed solution and the first-stage reaction slurry were both fed from the bottom of the fifth- to sixth-stage units at a rate of 5 mL / min. After stirring, the reaction was stopped when the pH reached 6.8, and the slurry finally overflowed to the seventh stage. The seventh-stage slurry underwent a maturation reaction, and the final maturation slurry was obtained after 1 hour.

[0078] (4) Solid-liquid separation: The matured slurry obtained in step (3) is filtered under vacuum to obtain ammonium chloride wastewater and filter cake. The filter cake is repeatedly washed with water to obtain praseodymium-neodymium fluorocarbonate (particle size D). 50 =28.92μm, (D 90 -D 10 ) / D 50 =1.5, fluorine conversion rate =99.8%.

[0079] Example 4

[0080] A method for the continuous preparation of large-particle rare earth fluorocarbonate and the co-production of nano-spherical silica using mixed fluorosilicone waste acid comprises the following steps:

[0081] (1) Silicon removal from mixed fluorosilicone waste acid: At room temperature, mixed fluorosilicone waste acid (F: 113.6 g / L, Si: 7.33 wt%) was added dropwise to an analytical grade 28% ammonia solution and stirred until the pH of the solution reached 9.0. The solution was then filtered using a vacuum filtration pump to obtain an alkaline fluorine-containing solution (F: 97.2 g / L, SiO2 < 0.01 g / L). The filter cake was solid SiO2 (particle size D). 50 =187.3nm, (D 90 -D 10 ) / D 50 =1.4).

[0082] (2) Compound 3M compound precipitation solution (nF - :nHCO3- = 0.26, nNH4HCO3:nNH4OH = 7:3): 1 L of the basic fluorine-containing solution was mixed with 7.3 L of a basic mixed solution (ammonium bicarbonate 1.55 Kg and 28 wt% ammonia water 634 mL were dissolved in deionized water and diluted to 7.3 L) at room temperature under stirring to form a complex precipitation solution.

[0083] (3) Continuous and co-current liquid phase precipitation reaction: the reaction temperature of the 1st-7th stage was controlled at 65°C, and the samarium chloride solution (C REO : 271 g / L) and the complex precipitation solution were fed from the bottom of the 1st stage device, the feeding speed of the samarium chloride solution was 25 mL / min, and the feeding speed of the complex precipitation solution was 14.6 mL / min. The reaction slurry was overflowed to the 2nd stage after stirring for 1 h 20 min. The complex precipitation solution was fed from the bottom of the 2nd-4th stage device, and the feeding speeds were 13.0 mL / min, 11.4 mL / min, and 9.7 mL / min, respectively. The reaction slurry was overflowed to the next stage after stirring. The basic mixed solution and the 1st stage reaction slurry were fed from the bottom of the 5th-6th stage device at a speed of 8 mL / min. The reaction was stopped after feeding until the pH was 6.8, and the slurry was finally overflowed to the 7th stage. The 7th stage slurry was subjected to a ripening reaction, and the final ripening slurry was obtained after 1 h.

[0084] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain ammonium chloride wastewater and a filter cake. The filter cake was repeatedly washed with water to obtain samarium fluocarbonate (particle size D 50 = 22.32 pm, (D 90 -D 10 ) / D 50 = 1.5, and the fluorine conversion rate = 99.7%).

[0085] Example 5

[0086] The method for continuously preparing large-particle rare earth fluocarbonate and co-producing nanometer spherical silica from fluorosilicon mixed waste acid is as follows:

[0087] (1) Removal of silicon from fluorosilicon mixed waste acid: under room temperature conditions, the fluorosilicon mixed waste acid (F: 128.0 g / L, Si: 7.26 wt%) was added dropwise to an analytical pure 28% ammonia solution under stirring until the pH of the solution was 8.7. A basic fluorine-containing solution (F: 101.3 g / L, SiO2< 0.01 g / L) was obtained by vacuum filtration with a filter pump, and the filter cake was SiO2 solid (particle size D 50 = 164.8 nm, (D 90 -D 10 ) / D 50 = 1.3).

[0088] (2) Preparation of a 3.5 M complex precipitation solution (nF - :nHCO3 -= 0.85, nNH4HCO3:nNH4OH = 7:3): 2 L of the basic fluorine-containing solution was mixed with 4.6 L of a basic mixed solution (1.62 Kg of ammonium bicarbonate and 659.4 mL of 28 wt% ammonia water were dissolved in deionized water and diluted to 4.6 L) at room temperature under stirring to form a complex precipitation solution.

[0089] (3) Continuous and co-current liquid phase precipitation reaction: the reaction temperature of the 1st to 7th stages was controlled at 70°C, and the lanthanum cerium nitrate solution (C REO : 283.5 g / L) and the complex precipitation solution were fed from the bottom of the 1st stage device, the feeding speed of the lanthanum cerium nitrate solution was 20.8 mL / min, and the feeding speed of the complex precipitation solution was 8.0 mL / min. The reaction slurry was overflowed to the 2nd stage reaction after stirring for 2 h. The complex precipitation solution was fed from the bottom of the 2nd to 4th stage devices, and the feeding speeds were 8.0 mL / min, 8.0 mL / min and 6.0 mL / min, respectively. The reaction slurry was overflowed to the next stage reaction after stirring. The basic mixed solution and the 1st stage reaction slurry were fed from the bottom of the 5th to 6th stage devices at a speed of 5 mL / min. The reaction was stopped after feeding when the pH was 6.8, and the slurry was finally overflowed to the 7th stage. The slurry of the 7th stage was subjected to a ripening reaction, and the final ripening slurry was obtained after 2 h.

[0090] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain ammonium nitrate wastewater and a filter cake. The filter cake was repeatedly washed with water to obtain lanthanum cerium fluocarbonate (particle size D 50 = 27.31 μm, (D 90 -D 10 ) / D 50 = 1.5, and fluorine conversion rate = 99.8%).

[0091] Example 6

[0092] The method for continuously preparing large-particle fluorocarbon rare earth carbonate and co-producing nanometer spherical silica from fluorosilicon mixed waste acid is as follows:

[0093] (1) Removal of silicon from fluorosilicon mixed waste acid: under room temperature, the fluorosilicon mixed waste acid (F: 128.0 g / L, Si: 7.26 wt%) was added dropwise into an analytical 28% ammonia water solution under stirring until the pH of the solution was 8.7. A basic fluorine-containing solution (F: 101.3 g / L, SiO2< 0.01 g / L) was obtained by vacuum filtration with a filter pump, and the filter cake was SiO2 solid (particle size D 50 = 178.3 nm, (D 90 -D 10 ) / D 50 = 1.5).

[0094] (2) Preparation of 3M complex precipitation solution (nF - :nHCO3 -= 0.6, nNH4HCO3:nNH4OH = 7:3): 1 L of the basic fluorine-containing solution was mixed with 3.7 L of a basic mixed solution (0.702 Kg of ammonium bicarbonate and 286 mL of 28 wt% ammonia water were dissolved in deionized water and diluted to 3.7 L) at room temperature under stirring to form a composite precipitation solution.

[0095] (3) Continuous and co-current liquid phase precipitation reaction: the reaction temperature of the 1st to 7th stages was controlled at 70°C, and the cerium sulfate solution (C REO : 28.2 g / L) and the composite precipitation solution were fed from the bottom of the 1st stage device, the feeding speed of the cerium sulfate solution was 100 mL / min, the feeding speed of the composite precipitation solution was 6.55 mL / min, and the reaction slurry was overflowed to the 2nd stage device after stirring for 40 min; the composite precipitation solution was fed from the bottom of the 2nd to 4th stage devices, and the feeding speeds were 4.4 mL / min, 3.3 mL / min and 2.2 mL / min, respectively; the reaction slurry was overflowed to the next stage after stirring; the basic mixed solution and the 1st stage reaction slurry were fed from the bottom of the 5th to 6th stage devices at a speed of 3 mL / min, the feeding was stopped after the reaction slurry was stirred to pH 6.8, and the slurry was finally overflowed to the 7th stage; the 7th stage slurry was subjected to a ripening reaction, and the final ripening slurry was obtained after 1 h.

[0096] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain ammonium sulfate wastewater and a filter cake, and the filter cake was repeatedly washed with water to obtain cerium fluocarbonate (particle size D 50 = 33.12 μm, (D 90 -D 10 ) / D 50 = 1.4, and the fluorine conversion rate = 99.8%).

[0097] Example 7

[0098] The method for continuously preparing large-particle fluorocarbon rare earth carbonate and co-producing nanometer spherical silica from fluorosilicon mixed waste acid is as follows:

[0099] (1) Removal of silicon from fluorosilicon mixed waste acid: under room temperature conditions, the fluorosilicon mixed waste acid (F: 128.0 g / L, Si: 7.26 wt%) was added dropwise into an analytical pure 28% ammonia water solution under stirring until the pH of the solution was 8.7, a basic fluorine-containing solution (F: 101.3 g / L, SiO2< 0.01 g / L) was obtained by vacuum filtration with a filter pump, and the filter cake was SiO2 solid (particle size D 50 = 176.8 nm, (D 90 -D 10 ) / D 50 = 1.5).

[0100] (2) Preparation of a 2.5 M composite precipitation solution (nF - :nHCO3 -= 0.5, nNH4HCO3: nNH4OH = 7:3): 1 L of the basic fluorine-containing solution was mixed with 5.4 L of a basic mixed solution (0.842 Kg of ammonium bicarbonate and 344 mL of 28 wt% ammonia water were dissolved in deionized water and diluted to 5.4 L) at room temperature under stirring to form a complex precipitation solution.

[0101] (3) Continuous and co-current liquid phase precipitation reaction: the reaction temperature of the 1st to 7th stages was controlled at 70°C, and the lanthanum acetate solution (C REO : 294 g / L) and the complex precipitation solution were fed from the bottom of the 1st stage device, the feeding speed of the lanthanum acetate solution was 20 mL / min, the feeding speed of the complex precipitation solution was 21.6 mL / min, and the reaction slurry was overflowed to the 2nd stage reaction after stirring for 1 h and 40 min; the complex precipitation solution was fed from the bottom of the 2nd to 4th stage devices, and the feeding speeds were 11.5 mL / min, 5.8 mL / min and 4.3 mL / min, respectively, and the reaction slurry was overflowed to the next stage reaction after stirring; the basic mixed solution and the 1st stage reaction slurry were fed from the bottom of the 5th to 6th stage devices at 10 mL / min, the feeding was stopped after the reaction slurry was stirred to pH 6.8, and the slurry was finally overflowed to the 7th stage; the 7th stage slurry was subjected to a ripening reaction, and the final ripening slurry was obtained after 1 h.

[0102] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain ammonium acetate wastewater and a filter cake, and the filter cake was repeatedly washed with water to obtain lanthanum fluocarbonate (particle size D 50 = 35.78 μm, (D 90 -D 10 ) / D 50 = 1.5, and fluorine conversion rate = 99.8%).

[0103] Example 8

[0104] The method for continuously preparing large-particle rare earth fluocarbonate and co-producing nanometer spherical silica from fluorosilicon mixed waste acid is as follows:

[0105] (1) Removal of silicon from fluorosilicon mixed waste acid: 30 wt% fluorosilicon acid was added dropwise to an analytical pure 28% ammonia water solution under room temperature, and the solution was stirred until the pH was 9.2, a basic fluorine-containing solution (F: 231.5 g / L, SiO2< 0.01 g / L) was obtained by vacuum filtration with a filter pump, and the filter cake was SiO2 solid (particle size D 50 = 150.3 nm, (D 90 -D 10 ) / D 50 = 1.3).

[0106] (2) Preparation of 3 M complex precipitation solution (nF - : nHCO3 -= 1, nNH4HCO3: nNH4OH = 7:3): 1 L of the basic fluorine-containing solution was mixed with 7.1 L of a basic mixed solution (0.963 Kg of ammonium bicarbonate and 393 mL of 28 wt% ammonia water were dissolved in deionized water and diluted to 7.1 L) to form a composite precipitation solution under stirring at room temperature.

[0107] (3) Continuous and co-current liquid phase precipitation reaction: the reaction temperature of the first to seventh stages was controlled at 65°C, and the cerium chloride solution (C REO : 285.6 g / L) and the composite precipitation solution were fed from the bottom of the first device, the feeding speed of the cerium chloride solution was 25 mL / min, and the feeding speed of the composite precipitation solution was 13.8 mL / min. The reaction slurry was overflowed to the second stage after stirring for 1 h and 40 min. The composite precipitation solution was fed from the bottom of the second to fourth devices, and the feeding speeds were 13.8 mL / min, 6.9 mL / min, and 6.9 mL / min, respectively. The reaction slurry was overflowed to the next stage after stirring. The basic mixed solution and the first-stage reaction slurry were fed from the bottom of the fifth to sixth devices at a speed of 8 mL / min. The reaction was stopped after feeding until the pH was 6.8, and the slurry was finally overflowed to the seventh stage. The slurry in the seventh stage was subjected to a ripening reaction, and the final ripening slurry was obtained after 1 h.

[0108] (4) Solid-liquid separation: the ripening slurry obtained in step (3) was subjected to vacuum filtration to obtain ammonium chloride wastewater and a filter cake. The filter cake was repeatedly washed with water to obtain cerium fluorocarbonate (particle size D 50 = 29.32 μm, (D 90 -D 10 ) / D 50 = 1.5, and the fluorine conversion rate = 99.8%).

[0109] Example 9

[0110] The types and concentrations of the raw materials were the same as in Example 1, the silicon removal in step (1), the preparation of the 3M composite precipitation solution in step (2), and the solid-liquid separation in step (4) were the same as in Example 1. The difference was in step (3). In this example, step (3) was: continuous and co-current liquid phase precipitation reaction: the reaction temperature of the first to seventh stages was controlled at 60°C, and the lanthanum cerium chloride solution (C REO: 266.58 g / L) and the complex precipitation solution was fed from the bottom of the first device, the feeding speed of the cerium lanthanum chloride solution was 83 mL / min, the feeding speed of the complex precipitation solution was 43.7 mL / min, and the reaction slurry was overflowed to the second reaction after stirring for 1 h; the complex precipitation solution was fed from the bottom of the second to fourth devices, and the feeding speeds were 43.7 mL / min, 22.0 mL / min and 22.0 mL / min, respectively, and the reaction slurry was overflowed to the next reaction after stirring; the basic mixed solution was fed from the bottom of the fifth to sixth devices at 20 mL / min, the feeding was stopped after the reaction slurry was stirred to pH 6.8, and the slurry was finally overflowed to the seventh device; the slurry in the seventh device was subjected to a ripening reaction (standing ripening), and the final ripening slurry was obtained after 1 h. In this embodiment, the first reaction slurry was not added to the fifth to sixth devices in step (3).

[0111] In this embodiment, the particle size D 50 of the lanthanum cerium fluocarbonate obtained in step (4) was 4.827 μm, (D 90 -D 10 ) / D 50 = 2.86, and the fluorine conversion rate was 99.6%.

[0112] It can be seen from the comparison of the results of Example 9 and Example 1 that the continuous precipitation reaction supplemented with the seed slurry can induce precipitation, which can further promote the growth of the rare earth fluocarbonate particles.

[0113] Comparative Example 1

[0114] The types and concentrations of the raw materials were the same as those in Example 1, the silicon removal in step (1) was the same as that in Example 1, the preparation of the 3M complex precipitation solution in step (2) was the same as that in Example 1, and the solid-liquid separation in step (4) was the same as that in Example 1, except that the single-tank precipitation reaction was used in step (3): the reaction temperature was controlled at 60°C, 1.2 L of the cerium lanthanum chloride solution (C REO : 266.58 g / L) was added dropwise into the bottom liquid containing 1 L of deionized water from the upper part of the reaction tank, the stirring reaction was started, the feeding speed of the cerium lanthanum chloride solution was 10 mL / min, and the feeding speed of the complex precipitation solution was 15.8 mL / min. After the feeding was completed, the basic mixed solution was added to adjust the pH of the reaction slurry to 6.8, and the final slurry was obtained after standing for 1 h.

[0115] In this comparative example, the particle size D 50 of the lanthanum cerium fluocarbonate obtained in step (4) was 4.827 μm, (D 90 -D 10 ) / D 50 = 2.86, and the fluorine conversion rate was 99.6%.

[0116] Comparative Example 2

[0117] The kind and concentration of the raw material of Example 1 are the same, and the silicon removal of the fluorosilicon mixed waste acid in step (1), the preparation of the 3M composite precipitation solution in step (2), and the solid-liquid separation in step (4) are the same, except that the single-tank seed-induced precipitation reaction is used in step (3): the reaction temperature is controlled at 60℃, 1.2L of lanthanum cerium chloride solution (C REO : 266.58g / L) and 1.9L of the composite precipitation solution are added dropwise from the upper part of the reaction tank to the bottom liquid, the bottom liquid is composed of 1L of deionized water and 71g of lanthanum cerium fluorocarbonate seed, the stirring reaction is started, the feeding speed of the lanthanum cerium chloride solution is 10mL / min, and the feeding speed of the composite precipitation solution is 15.8mL / min. After the feeding is completed, the alkaline mixed solution is added to adjust the pH of the reaction slurry to 6.8, and the final slurry is obtained after aging for 1h.

[0118] In the present comparative example, the particle size D 50 of the lanthanum cerium fluorocarbonate obtained in step (4) is 7.259μm, (D 90 -D 10 ) / D 50 =1.9, and the fluorine conversion rate is 99.7%.

[0119] By comparing the results of Comparative Example 1 and Example 1, it can be seen that the continuous precipitation reaction solves the problem of small particle size of the rare earth fluorocarbonate particles in the single-tank precipitation reaction.

[0120] By comparing the results of Comparative Example 2 and Example 1, it can be seen that the continuous precipitation reaction solves the problem of small particle size of the rare earth fluorocarbonate particles in the single-tank seed-induced precipitation reaction.

[0121] The above is only a preferred specific embodiment of the present application, and the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacements or changes to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for continuously preparing large particle rare earth fluorocarbon acid and co-producing nanometer spherical silicon dioxide by using fluorosilicon mixed waste acid, characterized in that, The method comprises the following steps: (1) removing silicon from fluorosilicon mixed waste acid: mixing fluorosilicon mixed waste acid with ammonia water to obtain a basic fluorine-containing solution and nanometer spherical silicon dioxide; (2) compounding a precipitant: compounding the basic fluorine-containing solution obtained in step (1) with a monobasic alkaline mixed solution to obtain a composite precipitation solution A; (3) continuous and concurrent precipitation: continuously precipitating the composite precipitation solution A obtained in step (2) with a soluble rare earth salt solution B; (4) solid-liquid separation: filtering the matured slurry obtained in step (3) to obtain the large-particle rare earth fluorocarbonate; The particle size D of the large particle fluorocarbon rare earth acid is 28-45 μm 50 ≥28 μm, the particle size range is (D 90 -D 10 ) / D 50 ≤1.5; In step (2), the monobasic alkaline mixed solution is selected from a mixed solution of carbonate and lye; the molar ratio of the alkaline fluoride solution in terms of F - and the monobasic alkaline mixed solution in terms of HCO3 - is (0.373-0.711):

1. In step (3), the continuous precipitation reaction comprises, in sequence, an induced nucleation process, a dielectric growth process, a terminal point control process and a maturation crystallization process; the continuous precipitation reaction is carried out in a continuous precipitation reaction device, the composite precipitation solution A and the soluble rare earth salt solution B are continuously added into the continuous precipitation reaction device, the continuous precipitation reaction device is sequentially divided into an induced nucleation unit, a dielectric growth unit, a terminal point control unit and a maturation crystallization unit, and the induced nucleation process, the dielectric growth process, the terminal point control process and the maturation crystallization process are respectively carried out, the feeding mode of each unit is from the bottom of the reaction device, and the reaction time of each unit is greater than or equal to 30 min; The induced nucleation unit is arranged as a first-stage reaction device, the composite precipitation solution A and the soluble rare earth salt solution B are added into the first-stage reaction device in a concurrent manner to carry out an induced nucleation reaction of rare earth fluorocarbonate, and the obtained first-stage crystal seed slurry automatically overflows into a next-stage reaction device; The dielectric growth unit is arranged as a second-stage to fourth-stage reaction device, the composite precipitation solution A is added into the second-stage to fourth-stage reaction device to carry out a dielectric growth reaction of the rare earth fluorocarbonate crystal nucleus, and the obtained growth slurry automatically overflows into a next-stage reaction device; The terminal point control unit is arranged as a fifth-stage to sixth-stage reaction device, which is provided with an on-line pH detector, the monobasic alkaline mixed solution and the first-stage crystal seed slurry are added into the fifth-stage to sixth-stage reaction device to carry out a complete precipitation reaction of rare earth, and the obtained complete precipitation slurry automatically overflows into a next-stage reaction device; The maturation crystallization unit is arranged as a seventh-stage reaction device, the overflow slurry of the previous stage is subjected to a maturation reaction to obtain a rare earth fluorocarbonate maturation slurry; The relative drop molar ratio of the complex precipitating solution A, calculated from the total amount of F - and HCO3 - , to the soluble rare earth salt solution B, calculated from the cation RE 3+ , is (0.33-2.07):1 in the 1st reaction device; the molar ratio of the total amount of the complex precipitating solution A, calculated from the total amount of F - and HCO3 - , to the soluble rare earth salt solution B, calculated from the total cation RE 3+ , is (0.93-2.67):1 in the 2nd-4th reaction devices. The terminal point of the complete precipitation reaction is controlled to be a pH value of 6.4-7.

2.

2. The method of claim 1, wherein, The primary particle size D of the nanospherical silica 50 ≤ 300 nm, with a particle size range of (D 90 - D 10 ) / D 50 ≤ 1.5; In step (1), the fluorosilicon mixed waste acid is selected from waste acid containing fluorosilicic acid or waste acid containing hydrofluoric acid and fluorosilicic acid, the content of fluorine in the fluorosilicon mixed waste acid is 90-250 g / L, and the content of silicon is 0.5-10 wt%; the pH value of the basic fluorine-containing solution obtained after the fluorosilicon mixed waste acid is mixed with ammonia water is controlled to be 7.2-9.5; In step (2), in the monobasic alkaline mixed solution, the carbonate is at least one selected from the group consisting of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate and sodium carbonate liquid or solid; and the lye is at least one selected from the group consisting of ammonia water and sodium hydroxide solution; In step (3), the soluble rare earth salt solution is selected from one of rare earth chlorides, rare earth sulfates, rare earth nitrates and rare earth acetates, and the temperature of the whole continuous precipitation reaction process is 25-80 ℃.

3. A large-particle rare earth fluorocarbonate prepared by the method according to claim 1.

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