A method for recovering rare earth from fluorinated rare earth solid waste

Abstract

The present invention relates to a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps: (1) ball milling mixed fluorinated rare earth solid waste, a conversion agent and a solvent, the obtained ball milled slurry is sequentially subjected to water leaching treatment and solid-liquid separation to obtain a fluorine-containing filtrate and a water leaching residue; (2) the water leaching residue obtained in step (1) is subjected to acid leaching treatment to obtain an acid leaching liquid and an acid leaching residue, the obtained acid leaching liquid is subjected to post-treatment to obtain a rare earth oxide; the fluorine-containing filtrate obtained in step (1) is mixed with an acid solution, and a fluorine-containing compound and a solvent are obtained by evaporation and crystallization, and the obtained solvent is recycled to step (1). The present invention improves the reaction activity of raw materials through the mechanochemical action of ball milling, promotes the efficient conversion of fluorinated rare earth into rare earth hydroxide, thereby achieving complete recovery of fluorine and rare earth, and the method has the characteristics of low cost and energy consumption, green environmental protection, etc.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource recovery, and in particular to a method for recovering rare earths from fluorinated rare earth solid wastes. Background Art

[0002] Rare earths are widely used in aerospace, weapons manufacturing, new energy, household appliances and other fields due to their unique and excellent optical, electrical and magnetic properties. With the increase in rare earth production and consumption, the output of solid waste containing rare earths has also increased. The random storage or landfill of solid waste not only wastes rare earth resources, but also causes very severe environmental pollution and ecological damage. Therefore, extracting and recovering rare earths from solid waste containing rare earths can alleviate the problems of rare earth mining and rare earth supply shortages, and can also reduce the environmental pollution caused by solid wastes.

[0003] It is difficult to extract rare earths from solid waste containing rare earth fluorides. Since rare earth fluorides are very stable in strong acids, it is difficult to extract rare earths from solid waste containing rare earth fluorides by conventional acid leaching methods. Usually, an alkaline leaching process is used to defluorinate the acid-insoluble rare earth fluorides and convert them into acid-soluble rare earth compounds. However, the newly generated rare earth hydroxides during the alkaline conversion of rare earth fluorides will "passivate" the rare earth fluorides, making it impossible for the rare earth fluorides to be completely converted into rare earth hydroxides. If the acid method is used directly to extract the rare earths from rare earth fluorides, a concentrated sulfuric acid roasting process is required to convert and remove the fluorine element in the rare earth fluorides in the form of hydrogen fluoride. However, this process has high equipment requirements, strong corrosiveness, high energy consumption, and large reagent consumption.

[0004] CN 113564343A discloses a green chemical alkali-to-defluorination method for roasting fluorine-containing rare earth ores and solid slag, including step 1, alkali-to-defluorination of conventional roasting fluorine-containing rare earth ores and slag, step 2, heating to extract NaF, step 3, solid-liquid separation, and step 4, heating to extract rare earth. CN 105316486A discloses a method for alkali-to-decomposition of metal electrolytic furnace waste slag containing rare earth fluoride, in order to recover rare earth in the electrolytic furnace containing rare earth fluoride, an excessive amount of concentrated alkali solution is mixed with the waste slag and then roasted and decomposed, the roasted product is added to a ball mill, and pure water is added to ball mill to dissolve sodium fluoride, and finally rare earth compounds are obtained. The above invention needs to be carried out under high temperature or concentrated alkali conditions, the consumption of reagents is large, and energy consumption is increased, and the subsequent wastewater treatment burden is increased.

[0005] CN 109161702A discloses a method for selectively extracting non-cerium rare earths from mixed rare earth concentrates, comprising: roasting a mixed rare earth concentrate containing bastnaesite and monazite in air oxidation at 400-650°C for 1-3 hours to generate a thermal oxidation roasted ore; oxidizing the trivalent cerium in the bastnaesite rare earth in the mixed rare earth concentrate to tetravalent cerium; mixing the thermal oxidation roasted ore with concentrated sulfuric acid, roasting at low temperature at 150-800°C for 0.5-2 hours, dissolving the oxidized roasted ore with concentrated sulfuric acid to form cerium phosphate and trivalent rare earth sulfate; the formed cerium phosphate and trivalent rare earth sulfate are subjected to water leaching and slurry adjustment, and solid-liquid separation to obtain a low-cerium rare earth sulfate solution and a cerium phosphate concentrate. However, the above process has the disadvantages of high energy consumption, large acid consumption, large wastewater discharge, and being unfriendly to the ecological environment.

[0006] In view of the shortcomings of the existing technology, there is an urgent need to provide a method that is low in energy consumption, green and environmentally friendly and can efficiently defluorinate and recover rare earths. Summary of the invention

[0007] The object of the present invention is to provide a method for recovering rare earth from fluorinated rare earth solid waste, which realizes the high-efficiency alkali conversion and defluorination of fluorinated rare earth at room temperature through the mechanochemical action of ball milling, obtains fluorine-containing compound byproducts, and finally realizes the high-efficiency acid leaching and dissolution of rare earth. The method has high efficiency, low energy consumption, low acid and alkali consumption, low wastewater generation and is green and environmentally friendly.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0010] (1) ball milling a mixture of fluorinated rare earth solid waste, a conversion agent, and a solvent, and subjecting the obtained ball milled slurry to water leaching and solid-liquid separation in turn to obtain a fluorine-containing filtrate and water leaching residue;

[0011] (2) The water leaching residue obtained in step (1) is subjected to acid leaching to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is subjected to post-treatment to obtain rare earth oxides;

[0012] The fluorine-containing filtrate obtained in step (1) is mixed with an acid solution, and then evaporated and crystallized to obtain a fluorine-containing compound and a solvent, and the obtained solvent is recycled and used in step (1).

[0013] The method provided by the present invention reduces the particle size of the material and increases the specific surface area through the mechanochemical action of the ball milling process, thereby correspondingly improving the reaction activity. At the same time, the "coating" of the rare earth fluoride by the impurities and the newly generated rare earth hydroxide is broken by the mechanical force, and the rare earth fluoride is efficiently converted into the rare earth hydroxide, thereby overcoming the problem that the rare earth fluoride needs to be converted with high temperature and concentrated alkali conditions. At the same time, the rare earth fluoride can be selectively converted with alkali, while other impurities are not converted with alkali, thereby greatly reducing the energy consumption and reagent consumption. In addition, the acid leaching solution does not contain fluoride ions, thereby avoiding the interference of fluorine in the subsequent rare earth impurity removal, separation and other processes, thereby improving the extraction rate of the rare earth and the recovery rate of the rare earth. In addition, the by-product fluorine-containing compounds can be recovered to reduce the generation of waste.

[0014] The acid leaching step in step (2) and the step of mixing the fluorine-containing filtrate with the acid solution are not preceded or followed in any particular order.

[0015] Preferably, the molar ratio of the conversion agent in step (1) to the rare earth fluoride in the rare earth fluoride solid waste is (1-6):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] If the ratio of the conversion agent to rare earth fluoride is too high, the conversion agent will be wasted and the amount of acid used will increase, thereby increasing costs; if the ratio is too low, the conversion of rare earth fluoride in the solid waste will be incomplete, resulting in a low rare earth leaching rate.

[0017] Preferably, the mass ratio of the total amount of the fluorinated rare earth solid waste and the conversion agent to the solvent in step (1) is 1:(0.2-8), for example, it can be 1:0.2, 1:0.5, 1:1, 1:3 or 1:8, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1:(0.5-3).

[0018] Preferably, the mass ratio of the balls mixed by ball milling in step (1) is 1:(10-50), for example, it can be 1:10, 1:20, 1:30, 1:40 or 1:50, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1:(30-50).

[0019] Preferably, the rotation speed of the ball milling mixing in step (1) is 200-800 rpm / min, for example, it can be 200 rpm / min, 500 rpm / min, 600 rpm / min, 700 rpm / min or 800 rpm / min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 500-800 rpm / min.

[0020] Preferably, the ball milling mixing time in step (1) is 10-180 min, for example, 10 min, 30 min, 50 min, 80 min or 180 min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 30-80 min.

[0021] Preferably, the ball milling mixing in step (1) is carried out in a planetary ball mill.

[0022] Preferably, the temperature of the ball milling mixing in step (1) is room temperature.

[0023] The fluoride rare earth solid waste in step (1) includes any one of fluoride rare earth smelting slag, fluoride rare earth ore, fluoride rare earth or fluoride rare earth molten salt electrolytic slag, or a combination of at least two of them. Typical but non-limiting combinations include a combination of fluoride rare earth smelting slag and fluoride rare earth ore, a combination of fluoride rare earth ore, fluoride rare earth and fluoride rare earth molten salt electrolytic slag, or a combination of fluoride rare earth smelting slag, fluoride rare earth ore, fluoride rare earth and fluoride rare earth molten salt electrolytic slag.

[0024] Preferably, the rare earth fluoride in the fluorinated rare earth solid waste in step (1) includes any one of dysprosium fluoride, yttrium fluoride, terbium fluoride, gadolinium fluoride, cerium fluoride, samarium fluoride, europium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride or lutetium fluoride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of dysprosium fluoride and gadolinium fluoride, a combination of europium fluoride, holmium fluoride, erbium fluoride and lutetium fluoride, or a combination of dysprosium fluoride, yttrium fluoride, terbium fluoride, gadolinium fluoride, cerium fluoride, samarium fluoride, europium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride.

[0025] Preferably, the conversion agent in step (1) comprises any one of sodium hydroxide, potassium hydroxide, calcium hydroxide or ammonia water, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of potassium hydroxide, calcium hydroxide and ammonia water, or a combination of sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonia water.

[0026] Preferably, the solvent in step (1) comprises water.

[0027] Preferably, the time of the water immersion treatment in step (1) is 5-120 min, for example, 5 min, 10 min, 30 min, 60 min or 120 min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 10-60 min.

[0028] Preferably, the temperature of the water immersion treatment in step (1) is 20-30°C, for example, 20°C, 22°C, 25°C, 28°C or 30°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the concentration of the acid used in the acid leaching treatment in step (2) is 0.01-10 mol / L, for example, 0.01 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L or 10 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable, preferably 0.5-3 mol / L.

[0030] Preferably, the acid used for the acid leaching treatment in step (2) comprises hydrochloric acid and / or nitric acid.

[0031] Preferably, the liquid-to-solid mass ratio of the acid leaching treatment in step (2) is (0.5-80):1, for example, it can be 0.5:1, 2:1, 20:1, 30:1 or 80:1, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably (2-30):1.

[0032] Preferably, the acid leaching time in step (2) is 5-150 min, for example, 5 min, 20 min, 30 min, 40 min or 150 min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 20-40 min.

[0033] Preferably, the post-treatment in step (2) includes a first post-treatment or a second post-treatment.

[0034] Preferably, the first post-treatment comprises extraction separation, precipitation treatment and precipitate incineration treatment performed in sequence.

[0035] Preferably, the second post-treatment comprises a precipitation treatment and a precipitate burning treatment performed sequentially.

[0036] Preferably, the precipitating agent used in the precipitation treatment includes oxalic acid.

[0037] Preferably, the acid solution comprises hydrofluoric acid.

[0038] The fluorine-containing filtrate mainly includes the remaining conversion agent and the fluorine-containing compound. The addition of hydrofluoric acid can completely convert the conversion agent into the fluorine-containing compound, so that the by-product fluorine-containing compound has a higher purity.

[0039] Preferably, the end point of the mixing is to make the fluorine-containing filtrate neutral.

[0040] Preferably, the fluorine-containing compound comprises any one of sodium fluoride, potassium fluoride, calcium fluoride or ammonium fluoride, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sodium fluoride and potassium fluoride, a combination of potassium fluoride, calcium fluoride and ammonium fluoride, or a combination of sodium fluoride, potassium fluoride, calcium fluoride and ammonium fluoride.

[0041] Preferably, the solvent comprises water.

[0042] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0043] (1) ball milling the mixed fluorinated rare earth solid waste, the conversion agent and the solvent at a speed of 200-800 rpm / min for 10-180 min, and the obtained ball milled slurry is sequentially treated with water at 20-30° C. for 5-120 min to separate the solid and liquid, thereby obtaining a fluorine-containing filtrate and a water-leached residue;

[0044] The molar ratio of the conversion agent to the rare earth fluoride in the rare earth fluoride solid waste is (1-6):1; the mass ratio of the total amount of the rare earth fluoride solid waste and the conversion agent to the solvent is 1:(0.2-8); the mass ratio of the ball milling mixture is 1:(10-50);

[0045] (2) The water leaching residue obtained in step (1) is treated with hydrochloric acid and / or nitric acid with a concentration of 0.01-10 mol / L for 5-150 min to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is post-treated to obtain rare earth oxides;

[0046] The liquid-to-solid mass ratio of the acid leaching treatment is (0.5-80):1; the post-treatment includes a first post-treatment or a second post-treatment; the first post-treatment includes extraction separation, precipitation treatment and precipitate burning treatment performed in sequence; the second post-treatment includes precipitation treatment and precipitate burning treatment performed in sequence;

[0047] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain a fluorine-containing compound and a solvent, and the obtained solvent is recycled to step (1).

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The method provided by the present invention reduces the particle size of the material and increases the specific surface area through the mechanochemical action of the ball milling process, thereby correspondingly improving the reaction activity and promoting the efficient conversion of rare earth fluoride into rare earth hydroxide, thereby overcoming the problem that rare earth fluoride requires high temperature and concentrated alkali conditions for alkali conversion, and can selectively convert rare earth fluoride into alkali; at the same time, the ball milling and acid leaching are both carried out at room temperature, the alkali conversion and acid leaching are fast and efficient, and the energy consumption and reagent consumption are greatly reduced;

[0050] (2) The method provided by the present invention avoids the generation of fluorine-containing waste gas and the discharge of fluorine-containing waste water, while ensuring the complete recovery of fluorine and rare earth. Since the acid leaching solution does not contain fluorine ions, fluorine interference in subsequent rare earth impurity removal and separation processes is avoided, thereby improving the extraction rate and recovery rate of rare earth. The rare earth leaching rate can reach 97.9% and the rare earth purity can reach 99.9%. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is the XRD diagram of the calcium thermal reduction yttrium fluoride smelting slag and the water leaching slag provided in Example 1 of the present invention;

[0052] Figure 2 is the XRD pattern of sodium fluoride provided in Example 1 of the present invention;

[0053] Figure 3 This is the XRD diagram of the acid leaching residue provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Example 1

[0056] This embodiment provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0057] (1) grinding a mixture of calcium thermal reduction yttrium fluoride smelting slag, sodium hydroxide and water in a planetary ball mill at room temperature and a rotation speed of 600 rpm / min for 50 minutes, and the obtained ball-milled slurry was successively subjected to water immersion treatment at 25° C. for 30 minutes and solid-liquid separation to obtain a fluorine-containing filtrate and water-leached slag;

[0058] The molar ratio of the sodium hydroxide to the yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag is 3:1; the mass ratio of the total amount of the calcium thermal reduction yttrium fluoride smelting slag and the sodium hydroxide to water is 1:1; the mass ratio of the ball milling mixture is 1:30;

[0059] (2) the water leaching residue obtained in step (1) is treated with 1 mol / L hydrochloric acid for 30 min to obtain an acid leaching solution and an acid leaching residue, and the obtained acid leaching solution is treated with oxalic acid precipitation and the precipitate is burned to obtain yttrium oxide; the liquid-to-solid mass ratio of the acid leaching treatment is 20:1;

[0060] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain sodium fluoride and water, and the obtained water is recycled to step (1).

[0061] The XRD patterns of the calcium thermal reduction yttrium fluoride smelting slag and the water leaching slag are as follows: Figure 1 As shown in FIG. 1 , the calcium thermal reduction yttrium fluoride smelting slag is composed of 71% CaF2, 23% YF3, 4% Y and 2% other impurities; the main component of the water-leached slag is Y(OH)3, indicating that the rare earth fluoride has been converted into rare earth hydroxide after ball milling and water leaching; the XRD pattern of the obtained sodium fluoride is shown in FIG. Figure 2 As shown in the figure, there is only the diffraction peak of sodium fluoride, indicating that the purity of sodium fluoride is high; the XRD diagram of the obtained acid leaching residue is as follows Figure 3 As shown, there is only the diffraction peak of calcium fluoride in the figure, indicating that the acid leaching residue is calcium fluoride with higher purity.

[0062] Example 2

[0063] This embodiment provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0064] (1) grinding a mixture of calcium thermal reduction yttrium fluoride smelting slag, sodium hydroxide and water in a planetary ball mill at room temperature and a rotation speed of 500 rpm / min for 80 minutes, and the obtained ball-milled slurry was successively subjected to water immersion treatment at 22° C. for 60 minutes and solid-liquid separation to obtain a fluorine-containing filtrate and water-leached slag;

[0065] The molar ratio of the sodium hydroxide to the yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag is 2:1; the mass ratio of the total amount of the calcium thermal reduction yttrium fluoride smelting slag and the sodium hydroxide to water is 1:0.5; the mass ratio of the ball milling mixture is 1:20;

[0066] (2) The water leaching residue obtained in step (1) is treated with hydrochloric acid at a concentration of 0.5 mol / L for 40 minutes to obtain an acid leaching solution and an acid leaching residue, and the obtained acid leaching solution is treated with oxalic acid precipitation and the precipitate is burned to obtain yttrium oxide; the liquid-to-solid mass ratio of the acid leaching treatment is 2:1;

[0067] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain sodium fluoride and water, and the obtained water is recycled to step (1).

[0068] Example 3

[0069] This embodiment provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0070] (1) grinding a mixture of calcium thermal reduction yttrium fluoride smelting slag, sodium hydroxide and water in a planetary ball mill at room temperature and a rotation speed of 700 rpm / min for 30 minutes, and the obtained ball-milled slurry was successively subjected to water immersion treatment at 28° C. for 10 minutes and solid-liquid separation to obtain a fluorine-containing filtrate and water-leached slag;

[0071] The molar ratio of the sodium hydroxide to the yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag is 4:1; the mass ratio of the total amount of the calcium thermal reduction yttrium fluoride smelting slag and the sodium hydroxide to water is 1:3; the mass ratio of the ball milling mixture is 1:40;

[0072] (2) The water leaching residue obtained in step (1) is treated with 3 mol / L hydrochloric acid for 20 min to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is treated with oxalic acid precipitation and the precipitate is burned to obtain yttrium oxide; the liquid-to-solid mass ratio of the acid leaching treatment is 30:1;

[0073] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain sodium fluoride and water, and the obtained water is recycled to step (1).

[0074] Example 4

[0075] This embodiment provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0076] (1) ball milling a mixture of calcium thermal reduction yttrium fluoride smelting slag, sodium hydroxide and water in a planetary ball mill at room temperature and a rotation speed of 200 rpm / min for 180 minutes, and the obtained ball mill slurry is successively subjected to 20° C. water immersion treatment for 120 minutes and solid-liquid separation to obtain a fluorine-containing filtrate and water leaching residue;

[0077] The molar ratio of the sodium hydroxide to the yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag is 1:1; the mass ratio of the total amount of the calcium thermal reduction yttrium fluoride smelting slag and the sodium hydroxide to water is 1:0.2; the mass ratio of the ball milling mixture is 1:10;

[0078] (2) the water leaching residue obtained in step (1) is treated with nitric acid at a concentration of 0.01 mol / L for 150 min to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is treated with oxalic acid precipitation and the precipitate is burned to obtain yttrium oxide; the liquid-to-solid mass ratio of the acid leaching treatment is 0.5:1;

[0079] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain sodium fluoride and water, and the obtained water is recycled to step (1).

[0080] Example 5

[0081] This embodiment provides a method for recovering rare earth from fluorinated rare earth solid waste, the method comprising the following steps:

[0082] (1) grinding a mixture of calcium thermal reduction yttrium fluoride smelting slag, sodium hydroxide and water in a planetary ball mill at room temperature at a rotation speed of 800 rpm / min for 10 minutes, and the obtained ball-milled slurry was successively subjected to water immersion treatment at 30° C. for 5 minutes and solid-liquid separation to obtain a fluorine-containing filtrate and water-leached slag;

[0083] The molar ratio of the sodium hydroxide to the yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag is 6:1; the mass ratio of the total amount of the calcium thermal reduction yttrium fluoride smelting slag and the sodium hydroxide to water is 1:8; the mass ratio of the ball milling mixture is 1:50;

[0084] (2) The water leaching residue obtained in step (1) is treated with nitric acid at a concentration of 10 mol / L for 5 minutes to obtain an acid leaching solution and an acid leaching residue, and the obtained acid leaching solution is treated with oxalic acid precipitation and the precipitate is burned to obtain yttrium oxide; the liquid-to-solid mass ratio of the acid leaching treatment is 80:1;

[0085] The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate becomes neutral, and then evaporated and crystallized to obtain sodium fluoride and water, and the obtained water is recycled to step (1).

[0086] Example 6

[0087] This embodiment provides a method for recovering rare earths from fluoride rare earth solid waste, which is different from Embodiment 1 in that, except for adjusting the molar ratio of sodium hydroxide to yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag in step (1) to 0.5:1, the rest is the same as Embodiment 1.

[0088] Example 7

[0089] This embodiment provides a method for recovering rare earths from fluoride rare earth solid waste, which is different from Embodiment 1 in that, except for adjusting the molar ratio of sodium hydroxide to yttrium fluoride in the calcium thermal reduction yttrium fluoride smelting slag in step (1) to 7:1, the rest is the same as Embodiment 1.

[0090] Example 8

[0091] This embodiment provides a method for recovering rare earths from fluorinated rare earth solid waste. The difference from Embodiment 1 is that the molar amount of the calcium thermal reduction yttrium fluoride smelting slag in step (1) is replaced by calcium thermal reduction terbium fluoride smelting slag, the terbium content in the calcium thermal reduction terbium fluoride smelting slag is 6%, and terbium oxide is obtained adaptively. The rest is the same as Embodiment 1.

[0092] Example 9

[0093] This embodiment provides a method for recovering rare earths from fluoride rare earth solid waste. The difference from Embodiment 1 is that the molar amount of the calcium thermal reduction yttrium fluoride smelting slag in step (1) is replaced by dysprosium fluoride, and the purity of the dysprosium fluoride is 99.9%. The molar amount of sodium hydroxide is replaced by potassium hydroxide, and potassium fluoride and dysprosium oxide are obtained adaptively. The rest is the same as Embodiment 1.

[0094] Example 10

[0095] This embodiment provides a method for recovering rare earths from fluoride rare earth solid waste. The difference from Embodiment 1 is that the molar amount of the calcium thermal reduction yttrium fluoride smelting slag in step (1) is replaced by fluoride rare earth molten salt electrolytic slag, and the acid leaching solution obtained in step (2) is subjected to extraction separation, oxalic acid precipitation treatment and precipitate burning treatment to obtain cerium oxide, samarium oxide and europium oxide. The rest is the same as Embodiment 1.

[0096] Comparative Example 1

[0097] This comparative example provides a method for recovering rare earths from fluorinated rare earth solid wastes. The difference from Example 1 is that except that the ball milling mixing in step (1) is adjusted to conventional stirring at the same speed, the rest is the same as Example 1.

[0098] The acid leaching solutions provided in Examples 1-10 and Comparative Example 1 were used to calculate the rare earth leaching rate η using (Formula 1), and the results are shown in Table 1; the purity of rare earth oxide was tested using the "Chemical Analysis Methods for Non-Rare Earth Impurities in Rare Earth Metals and Their Oxides" (GB / T12690) series of standards and the "Chemical Analysis Methods for Rare Earth Impurities in Rare Earth Metals and Their Oxides" (GB / 18115) series of standards, and the results are shown in Table 1.

[0099]

[0100] Table 1

[0101]

[0102]

[0103] As can be seen from Table 1, by comparing Example 1 with Examples 2-5, it can be seen that the method provided by the present invention can obtain a higher rare earth leaching rate by setting a reasonable raw material ratio and optimizing the ball milling process and water leaching and acid leaching process parameters. The purity of the obtained rare earth oxide can reach 99.9%, the process energy consumption and cost are low, and it is green and environmentally friendly.

[0104] By comparing Example 1 with Examples 6 and 7, it can be seen that the ratio of the conversion agent to the rare earth fluoride needs to be controlled within a reasonable range. If the ratio is too low, the rare earth fluoride conversion is incomplete and the rare earth leaching rate is low; if the ratio is too high, although the rare earth leaching rate is slightly improved, the conversion agent and the acid solution are wasted; by comparing Example 1 with Examples 8-10, it can be seen that by using other types of rare earth fluoride solid wastes to recover rare earths and fluorides, a higher rare earth leaching rate can also be obtained, and the purity of the obtained rare earth oxide can also be guaranteed;

[0105] From the comparison between Example 1 and Comparative Example 1, it can be seen that the ordinary stirring procedure for mixing the raw materials cannot improve the reaction activity of the materials, and the rare earth fluoride cannot be completely converted into rare earth hydroxide, resulting in a significant decrease in the rare earth leaching rate.

[0106] In summary, the method provided by the present invention reduces the particle size of the material and increases the specific surface area through the mechanochemical action of the ball milling process, thereby correspondingly improving the reaction activity and promoting the efficient conversion of rare earth fluoride into rare earth hydroxide, thereby overcoming the problem that rare earth fluoride requires high temperature and concentrated alkali conditions for alkali conversion, and can selectively convert rare earth fluoride into alkali; at the same time, the ball milling and acid leaching are both carried out at room temperature, the alkali conversion and acid leaching are fast and efficient, and the energy consumption and reagent consumption are greatly reduced;

[0107] The method provided by the present invention avoids the generation of fluorine-containing waste gas and the discharge of fluorine-containing waste water, and at the same time ensures the complete recovery of fluorine and rare earth. Since the acid leaching solution does not contain fluorine ions, fluorine interference in subsequent rare earth impurity removal, separation and other processes is avoided, and the extraction rate and recovery rate of rare earth are improved. The rare earth leaching rate can reach 97.9%, and the rare earth purity can reach 99.9%.

[0108] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recovering rare earth from fluorinated rare earth solid waste, characterized in that: The method comprises the following steps: (1) ball milling a mixture of fluorinated rare earth solid waste, a conversion agent, and a solvent at room temperature, and subjecting the obtained ball milled slurry to water leaching and solid-liquid separation in turn to obtain a fluorine-containing filtrate and water leaching residue; (2) The water leaching residue obtained in step (1) is subjected to acid leaching treatment at room temperature to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is post-treated to obtain rare earth oxides; the temperature of the water leaching treatment in step (1) is 20-30° C.; the molar ratio of the conversion agent in step (1) to the rare earth fluoride in the rare earth fluoride solid waste is (3-4):1; The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate is neutral, and the fluorine-containing compound and the solvent are obtained by evaporation and crystallization, and the obtained solvent is recycled to step (1); The post-processing in step (2) includes a first post-processing or a second post-processing; The first post-treatment includes extraction separation, precipitation treatment and precipitation burning treatment performed in sequence; The second post-treatment includes a precipitation treatment and a precipitate burning treatment performed in sequence; The precipitant used in the precipitation treatment is oxalic acid.

2. The method according to claim 1, characterized in that In step (1), the mass ratio of the total amount of the rare earth fluoride solid waste and the conversion agent to the solvent is 1:(0.2-8).

3. The method according to claim 2, characterized in that In step (1), the mass ratio of the total amount of the rare earth fluoride solid waste and the conversion agent to the solvent is 1:(0.5-3).

4. The method according to claim 1, characterized in that: The mass ratio of the balls mixed by ball milling in step (1) is 1:(10-50).

5. The method according to claim 4, characterized in that The mass ratio of the balls mixed by ball milling in step (1) is 1:(30-50).

6. The method according to claim 1, characterized in that The rotation speed of the ball milling mixing in step (1) is 200-800 rpm / min.

7. The method according to claim 6, characterized in that The rotation speed of the ball milling mixing in step (1) is 500-800 rpm / min.

8. The method according to claim 1, characterized in that The ball milling mixing time in step (1) is 10-180 minutes.

9. The method according to claim 8, characterized in that The ball milling mixing time in step (1) is 30-80 minutes.

10. The method according to claim 1, characterized in that The rare earth fluoride solid waste in step (1) includes any one of rare earth fluoride smelting slag, rare earth fluoride ore, rare earth fluoride or rare earth fluoride molten salt electrolytic slag, or a combination of at least two of them.

11. The method according to claim 10, characterized in that The rare earth fluoride in the rare earth fluoride solid waste in step (1) includes any one of dysprosium fluoride, yttrium fluoride, terbium fluoride, gadolinium fluoride, cerium fluoride, samarium fluoride, europium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride or lutetium fluoride, or a combination of at least two thereof.

12. The method according to claim 1, characterized in that The conversion agent in step (1) includes any one of sodium hydroxide, potassium hydroxide, calcium hydroxide or ammonia water, or a combination of at least two of them.

13. The method according to claim 1, characterized in that The solvent in step (1) includes water.

14. The method according to claim 1, characterized in that The time of the water immersion treatment in step (1) is 5-120 minutes.

15. The method according to claim 14, characterized in that The time of the water immersion treatment in step (1) is 10-60 minutes.

16. The method according to claim 1, characterized in that The concentration of the acid used in the acid leaching treatment in step (2) is 0.01-10 mol / L.

17. The method according to claim 16, characterized in that The concentration of the acid used in the acid leaching treatment in step (2) is 0.5-3 mol / L.

18. The method according to claim 1, characterized in that The acid used for the acid leaching treatment in step (2) includes hydrochloric acid and / or nitric acid.

19. The method according to claim 1, characterized in that The liquid-to-solid mass ratio of the acid leaching treatment in step (2) is (0.5-80):

1.

20. The method according to claim 19, characterized in that The liquid-to-solid mass ratio of the acid leaching treatment in step (2) is (2-30):

1.

21. The method according to claim 1, characterized in that The acid leaching treatment time in step (2) is 5-150 minutes.

22. The method according to claim 21, characterized in that The acid leaching treatment time in step (2) is 20-40 minutes.

23. The method according to claim 1, characterized in that The fluorine-containing compound includes any one of sodium fluoride, potassium fluoride, calcium fluoride or ammonium fluoride, or a combination of at least two of them.

24. The method according to claim 1, characterized in that The solvent obtained by evaporative crystallization includes water.

25. The method according to claim 1, characterized in that The method comprises the following steps: (1) ball milling the mixed fluorinated rare earth solid waste, the conversion agent and the solvent at a speed of 200-800 rpm / min for 10-180 min, and the obtained ball milled slurry is sequentially treated with water at 20-30° C. for 5-120 min to separate the solid and liquid, thereby obtaining a fluorine-containing filtrate and a water-leached residue; The molar ratio of the conversion agent to the rare earth fluoride in the rare earth fluoride solid waste is (3-4):1; the mass ratio of the total amount of the rare earth fluoride solid waste and the conversion agent to the solvent is 1:(0.2-8); the mass ratio of the ball milling mixture is 1:(10-50); (2) The water leaching residue obtained in step (1) is treated with hydrochloric acid and / or nitric acid with a concentration of 0.01-10 mol / L for 5-150 min to obtain an acid leaching solution and acid leaching residue, and the obtained acid leaching solution is post-treated to obtain rare earth oxides; The liquid-to-solid mass ratio of the acid leaching treatment is (0.5-80):1; the post-treatment includes a first post-treatment or a second post-treatment; the first post-treatment includes extraction separation, precipitation treatment and precipitate burning treatment performed in sequence; the second post-treatment includes precipitation treatment and precipitate burning treatment performed in sequence; The fluorine-containing filtrate obtained in step (1) is mixed with hydrofluoric acid until the fluorine-containing filtrate is neutral, and the fluorine-containing compound and the solvent are obtained by evaporation and crystallization, and the obtained solvent is recycled to step (1); The precipitant used in the precipitation treatment is oxalic acid.

Images