Dissolution of rare earth metals and related systems

Abstract

Methods of dissolving rare-earth metals in liquids are generally provided.

Description

[0001] DISSOLUTION OF RARE EARTH METALS AND RELATED SYSTEMS

[0002] RELATED APPLICATIONS

[0003] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 587,434, filed October 2, 2023, and entitled “Process and System for Dissolving REO Feed Materials,” which is incorporated herein by reference in its entirety for all purposes.

[0004] TECHNICAL FIELD

[0005] Methods of dissolving rare-earth metals in liquids generally described.

[0006] SUMMARY

[0007] Methods of dissolving rare-earth metals in liquids are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0008] Certain aspects are related to methods of dissolving a rare-earth metal in a liquid.

[0009] In some embodiments, a method comprises feeding a solid material comprising the rare-earth metal into the liquid, wherein: the liquid is contained in a container, the container further contains a gaseous atmosphere positioned above and in fluidic communication with the liquid, a pressure of the gaseous atmosphere is less than or equal to 1 atm absolute, and the solid material is fed at a rate of greater than or equal to 0.1 g / min and less than or equal to 500 tons / min.

[0010] In some embodiments, the method comprises feeding a solid material comprising the rare-earth metal into the liquid, wherein: the liquid is contained in a container, the container is enclosed in a reactor further comprising a gaseous atmosphere positioned above and in fluidic communication with the liquid, a pressure of the gaseous atmosphere is less than or equal to 1 atm absolute, and the solid material is fed at a rate of greater than or equal to 0.1 g / min and less than or equal to 500 tons / min.

[0011] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0014] FIG. 1 is, in accordance with certain embodiments, a schematic illustration of a flow chart showing a method.

[0015] FIGs. 2A-2C are, in accordance with some embodiments, cross-sectional schematic illustrations of systems in which a solid material is being fed into a liquid.

[0016] FIG. 3 is a cross-sectional schematic illustration of a vessel in which methods according to certain embodiments can be performed.

[0017] FIG. 4 is, in accordance with certain embodiments, a cross-sectional schematic illustration of a system comprising a gas scrubber.

[0018] FIG. 5 is, in accordance with certain embodiments, a photograph of a container containing a liquid into which a solid comprising a rare-earth metal is fed.

[0019] DETAILED DESCRIPTION

[0020] Methods of dissolving rare-earth metals in liquids are generally provided.

[0021] In some embodiments, a rare-earth metal that is being dissolved in a liquid is initially present in a solid material. The solid material may also comprise an impurity metal, and, in some such embodiments, the impurity metal either is dissolved at a substantially lower rate than the rare-earth metal (e.g., does not dissolve) and / or is dissolved and then precipitated from the liquid. In such embodiments, dissolving the rare-earth metal in a liquid may also assist with separating the impurity metal from the rare-earth metal. In some embodiments, a rare-earth metal is dissolved in a liquid in a manner that advantageously results in the formation of a relatively low number of gas bubbles, the extraction of any gas bubbles that do form relatively rapidly, and / or the formation of a relatively low number and / or volume of splashes. Advantageously, the formation of a relatively low number of gas bubbles and / or the rapid removal of gas bubbles may reduce the loss of time associated with removing gas bubbles from the liquid subsequent to dissolution. The formation of a relatively low number of gas bubbles, their rapid removal, and the formation of a relatively low number and / or volume of splashes may reduce loss of the liquid due to gas bubble-induced overflow and / or splashing of the solution out of the container in which dissolution is occurring.

[0022] In some embodiments, a rare-earth metal is dissolved in a liquid in a manner that has one or more of the advantageous properties described herein (e.g., low ultimate dissolution of an impurity metal, low bubbling and / or splashing) and is also fed into the liquid and / or dissolved in the liquid at a relatively high rate. This may advantageously assist with enhancing the throughput during downstream rare-earth separation and / or purification processes performed on the liquid into which the rare-earth metal is dissolved.

[0023] FIG. 1 depicts one exemplary method. In FIG. 1, the method 100 comprises the step 102 of feeding a solid material comprising a rare-earth metal into a liquid. The feeding may occur in any suitable manner. For instance, it may be with the assistance of a conveyor belt, a chute, a hopper, and / or a feeder. Some or all of such components may be formed of steel. The feeding may be performed at any suitable location with respect to the liquid. For instance, in some embodiments, the feeding may be performed at a location where the liquid is undergoing a relatively high degree of mixing (e.g., proximate to an impeller stirring the liquid, proximate to a vortex formed in the liquid). It is also possible for feeding to be performed into a liquid that is not being mixed. In some embodiments, the feeding may be performed through a gaseous atmosphere (e.g., a gaseous atmosphere positioned above and in fluidic communication with the liquid and / or a container in which it is contained) into the liquid.

[0024] In some such embodiments, a liquid into which a solid material is fed may be present in an environment that promotes the dissolution of the rare-earth metal in an advantageous manner described herein. As one example, in some embodiments, a solid material may be fed into the liquid in the presence of air. The air may oxidize one or more impurity metals present in the solid material and / or may oxidize one or more components that, when oxidized, form complexes with one or more impurity metals present in the solid material. Without wishing to be bound by any particular theory, it is believed that such oxidation and / or complex formation may suppress dissolution in the liquid of impurity metals present in the solid material. It is also believed that such oxidation and / or complex formation may facilitate the precipitation from the liquid of any such impurity metals that are initially dissolved in the liquid. For instance, it may facilitate the reduction of any impurity metal ions that become solubilized in the liquid, resulting in their precipitation in metallic and / or alloyed form (e.g., in a form having a zero oxidation state).

[0025] As another example, in some embodiments, liquid into which a solid material is fed is enclosed in a container (e.g., a reactor) further containing and / or comprising a gaseous atmosphere that has one or more advantageous properties. The gaseous atmosphere may be positioned above and / or in fluidic communication with the liquid. It is also possible for the gaseous atmosphere to be positioned above and / or in fluidic communication with a container positioned in the reactor that contains the liquid (e.g., a container in which the liquid is contained). In some embodiments, a single container (e.g., a reactor) contains both the liquid and the gaseous atmosphere.

[0026] In some embodiments, the gaseous atmosphere has a relatively low pressure (e.g., a pressure below atmospheric pressure and / or below 1 atm absolute). Without wishing to be bound by any particular theory, it is believed that the presence of a relatively low pressure in such a gaseous atmosphere may suppress the formation of gas bubbles in the liquid and / or may assist with removing from the liquid any gas bubbles that do form therein. It is also believed that the presence of a relatively low pressure in such a gaseous atmosphere may facilitate the removal of the gas bubbles without popping and / or with rapid popping. As gas bubbles present on the surface may prevent uniform feeding of a solid material into the liquid, and feeding that is too rapid may cause spillage of the liquid from its container due to splashing and / or the release of heat, the removal of gas bubbles in this manner may be desirable.

[0027] In some embodiments, a method comprises a further step in addition to the feeding of the solid material into the liquid. Two examples of such steps, shown in FIG. 1 by reference signs 104 and 106, respectively, are the dissolution of an impurity metal initially present in the solid material in the liquid and the precipitation of the dissolved impurity metal from the liquid. As noted above, in some embodiments, the environment in which the solid material is fed into the liquid may facilitate this precipitation. In some embodiments, the precipitates formed by this precipitation may be relatively soluble in one or more liquids (e.g., an aqueous fluid having an appropriate pH value), and may be further removed from the liquid and / or its container by dissolution in such a liquid subsequent to the dissolution of the rare-earth metal in the liquid.

[0028] Additionally, although FIG. 1 shows the performance of steps 104 and 106 after step 102 (and it is possible for these steps to be performed in this sequence), it is possible for these steps to be performed during periods of time that overlap. For instance, a solid material may be fed into a liquid over a period of time and impurity metal that is present in solid material fed into the liquid earlier may undergo dissolution in the liquid and / or precipitation therefrom while further solid material is being fed into the liquid.

[0029] It should also be noted that it is not required for a solid comprising a rare-earth metal being dissolved in a liquid to include any impurity metals that are soluble in the liquid, any impurities metals at all, and / or any other impurities. In such embodiments, steps 104 and 106 of FIG. 1 would not be performed.

[0030] One further example of an optional step that may be performed in some embodiments is mixing the liquid. This step is shown in FIG. 1 by reference sign 108. Although FIG. 1 shows the performance of step 108 after steps 102, 104, and 106 (and it is possible for these steps to be performed in this sequence), it is possible for these steps to be performed during periods of time that overlap and / or for the mixing to be performed first. For instance, a solid material may be fed into a liquid that is being mixed and / or an impurity metal may be dissolved in and / or precipitate from a liquid that is being mixed. It is also possible for feeding and mixing steps to be performed separately (e.g., a rare-earth metal-containing solid material may be fed into a liquid that is not being mixed and, subsequent to the feeding, the liquid may be mixed; a rare-earth metal-containing solid material may be fed into a liquid that is being mixed and, subsequent to the feeding, the liquid may continue to be mixed).

[0031] FIG. 2A shows one non-limiting example of a system in which a solid material is being fed into a liquid. In FIG. 2A, the system 210 comprises a container 212 containing a liquid 214. The container 212 further contains a gaseous atmosphere 216 positioned above and in fluidic communication with the liquid 214. In FIG. 2A, the solid material 218 is being fed into the liquid 214. In some embodiments, like the embodiment shown in FIG. 2A, a solid material may be fed into a liquid through a gaseous atmosphere positioned above and in fluidic communication with the liquid. It is also possible for a solid material to be fed into a liquid in other manners.

[0032] As noted above, in some embodiments, a solid material is dissolved into a liquid into which it is fed. This is shown schematically in FIG. 2B, which depicts the dissolution of a particle 218A of solid material 218 into the liquid 214 into which it is being fed. FIG. 2B also depicts the system 210 and the gaseous atmosphere 216.

[0033] FIG. 2C shows one non-limiting example of a system in which a liquid is contained in a container and the container is enclosed in a reactor. In FIG. 2C, the system 210 comprises a reactor 220 containing a container 212. The container 212 further contains a liquid 214 and a gaseous atmosphere 216, the latter above and in fluidic communication with the liquid 214. FIG. 2C also shows a solid material 218 being fed into the liquid 4=214.

[0034] FIG. 3 shows one non-limiting example of an embodiment in which a solid material is fed into a liquid as the liquid is being mixed. In FIG. 3, the liquid is mixed by stirring, but other methods of mixing are also possible. As also shown in FIG. 3, during these processes, an impurity metal present in the solid material is dissolving in the liquid and then precipitating therefrom. The precipitation shown in FIG. 3 takes the form of particulates comprising the impurity metal at the bottom of the container in which the liquid is positioned. FIG. 3 also shows several further optional features that may be present during the performance of a method described herein. These include the solid material taking the form of a powder, the use of a hopper to supply the solid material, the formation of a vortex in the liquid being mixed, and the removal of gas from the reactor to a location downstream (e.g., a gas scrubber) for treatment.

[0035] FIG. 4 further shows an example of a system comprising a gas scrubber. In FIG. 4, the system 410 comprises a container 412 that is in fluidic communication with a gas scrubber 422. As shown in FIG. 4, fluidic communication between a container and a gas scrubber may be effectuated by a fluidic conduit, such as tubing. As noted above, some embodiments relate to feeding a solid material comprising a rare-earth metal into a liquid. The feeding may be performed at a variety of suitable rates. In some embodiments, the feeding is performed at a rate of greater than or equal to 0.1 g / min, greater than or equal to 0.2 g / min, greater than or equal to 0.5 g / min, greater than or equal to 0.75 g / min, greater than or equal to 1 g / min, greater than or equal to 2 g / min, greater than or equal to 5 g / min, greater than or equal to 7.5 g / min, greater than or equal to 10 g / min, greater than or equal to 20 g / min, greater than or equal to 50 g / min, greater than or equal to 75 g / min, greater than or equal to 100 g / min, greater than or equal to 200 g / min, greater than or equal to 500 g / min, greater than or equal to 750 g / min, greater than or equal to 1 kg / min, greater than or equal to 2 kg / min, greater than or equal to 5 kg / min, greater than or equal to 7.5 kg / min, greater than or equal to 10 kg / min, greater than or equal to 20 kg / min, greater than or equal to 50 kg / min, greater than or equal to 75 kg / min, greater than or equal to 100 kg / min, greater than or equal to 200 kg / min, greater than or equal to 500 kg / min, greater than or equal to 750 kg / min, greater than or equal to 1 ton / min, or greater than or equal to 2 tons / min. In some embodiments, the feeding is performed at a rate of less than or equal to 5 tons / min, less than or equal to 2 to tons / min, less than or equal to 1 ton / min, less than or equal to 750 kg / min, less than or equal to 500 kg / min, less than or equal to 200 kg / min, less than or equal to 100 kg / min, less than or equal to 75 kg / min, less than or equal to 50 kg / min, less than or equal to 20 kg / min, less than or equal to 10 kg / min, less than or equal to 7.5 kg / min, less than or equal to 5 kg / min, less than or equal to 2 kg / min, less than or equal to 1 kg / min, less than or equal to 750 g / min, less than or equal to 500 g / min, less than or equal to 200 g / min, less than or equal to 100 g / min, less than or equal to 75 g / min, less than or equal to 50 g / min, less than or equal to 20 g / min, less than or equal to 10 g / min, less than or equal to 7.5 g / min, less than or equal to 5 g / min, less than or equal to 2 g / min, less than or equal to 1 g / min, less than or equal to 0.75 g / min, less than or equal to 0.5 g / min, or less than or equal to 0.2 g / min. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 g / min and less than or equal to 5 tons / min). Other ranges are also possible.

[0036] The feeding may be performed for a variety of suitable times. In some embodiments, the feeding is performed for a period of time of greater than or equal to 30 minutes, greater than or equal to 1 hour, greater than or equal to 1.5 hours, greater than or equal to 2 hours, greater than or equal to 2.5 hours, greater than or equal to 3 hours, or greater than or equal to 3.5 hours. In some embodiments, the feeding is performed for a period of time of less than or equal to 4 hours, less than or equal to 3.5 hours, less than or equal to 3 hours, less than or equal to 2.5 hours, less than or equal to 2 hours, less than or equal to 1.5 hours, or less than or equal to 1 hour. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 30 minutes and less than or equal to 4 hours, or greater than or equal to 30 minutes and less than or equal to 2 hours).

[0037] Other ranges are also possible.

[0038] As noted above, one or more (e.g., two or more) rare-earth metals may be dissolved in the liquids described herein. The “rare-earth metals,” as used herein, are the lanthanides, yttrium (Y), and scandium (Sc). The “lanthanides,” as used herein, are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). In some embodiments, one or more of the following rare-earth metals preferentially dissolves in a liquid in comparison to one or more impurity metals: Y, Sc, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0039] In some embodiments, a rare-earth metal-containing solid material further comprises one or more (e.g., two or more) impurity metals. Non-limiting examples of suitable impurity metals include aluminum (Al), cerium (Ce), copper (Cu), iron (Fe), and calcium (Ca). As can be seen from the inclusion of Ce, it is possible for an impurity metal to be a rare-earth metal, such as a rare-earth metal that is not desired to be recovered. In such embodiments, one rare-earth metal may be preferentially dissolved in a liquid in comparison to a different rare-earth metal, and the rare-earth metal that is not preferentially dissolved in the liquid may be considered to be an impurity metal.

[0040] In some embodiments, Ce is oxidized by oxygen present prior to and / or during the feeding of the solid material into the liquid. In such instances, it may have an oxidation state of 4+. Such Ce may complex with Al. In such instances, a solid may precipitate and / or fail to dissolve that comprises both Ce and Al.

[0041] In some embodiments, a rare-earth metal-containing solid further comprises one or more (e.g., two or more) impurities that are not metals. Non-limiting examples of such impurities include sulfur (S) and silicon (Si). Rare-earth metals and impurity metals may be present in the solid materials described herein in a variety of suitable forms. In some embodiments, a solid material described herein comprises a compound comprising a rare-earth metal (and, possibly, an impurity metal) that is a carbonate, an oxide, and / or a hydroxide.

[0042] Rare-earth metal-containing solids may comprise a variety of suitable species. Non-limiting examples of such species include La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, sodium (Na), Ca, Cu, S, Si, Fe, Y, Sc, Sr, Er, Ni, and manganese (Mn).

[0043] In some embodiments, a rare-earth metal-containing solid has a total rare-earth oxide content that is relatively high. In some embodiments, rare-earth metal oxides make up greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, greater than or equal to 90 wt%, greater than or equal to 95 wt%, or greater than or equal to 99 wt% of the rare-earth metal-containing solid. In some embodiments, rare- earth metal oxides make up less than or equal to 99.9 wt%, less than or equal to 99 wt%, less than or equal to 95 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, or less than or equal to 20 wt% of the rare-earth metal-containing solid. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 99.9 wt%). Other ranges are also possible.

[0044] In some embodiments, a rare-earth metal-containing solid comprises a relatively large amount of Nd and Pr. In some embodiments, Nd oxides, Pr oxides, and NdPr oxides together make up greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, greater than or equal to 90 wt%, greater than or equal to 95 wt%, or greater than or equal to 99 wt% of the rare-earth metal oxides present in the rare-earth metal-containing solid. In some embodiments, Nd oxides, Pr oxides, and NdPr oxides together make up less than or equal to 99.9 wt%, less than or equal to 99 wt%, less than or equal to 95 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, or less than or equal to 20 wt% of the rare-earth metal oxides present in the rare-earth metal-containing solid. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 15 wt% and less than or equal to 99.9 wt%). Other ranges are also possible.

[0045] In some embodiments, a rare-earth metal-containing solid comprises water. The water may make up greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, or greater than or equal to 45 wt% of the rare-earth metal-containing solid. The water may make up less than or equal to 50 wt%, less than or equal to 45 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, or less than or equal to 0.2 wt% of the rare-earth metal-containing solid. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 50 wt%). Other ranges are also possible.

[0046] After a rare-earth metal-containing solid is fed into a liquid described herein, a variety of suitable species present in the rare-earth metal-containing solid may fail to dissolve and / or fail to fully dissolve (e.g., less than 75 wt%, less than 50 wt%, less than 25 wt%, less than 10 wt%, less than 5 wt%, less than 2 wt%, less than 1 wt%, or less (e.g., of impurities) may dissolve) in the liquid or may dissolve in the liquid and then precipitate therefrom. Non-limiting examples of such species include Ce, Nd, La, Pr, S, Sm, Cu, Gd, Tb, Fe, Eu, Y, Dy, Si, Ca, Sc, Sr, Er, Yb, Mn, and Ni. In some such embodiments, the rare-earth metal that is desired to be recovered may dissolve to a relatively large degree (e.g., such that at least 50 wt%, at least 75 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt%, or all of the rare-earth metal that is desired to be recovered dissolves). In some embodiments, an element present in a rare-earth metal-containing solid (e.g., an impurity metal therein, a rare-earth metal therein) does not fully dissolve in a liquid. For instance, such an element may partially dissolve in a liquid. It may also partially fail to dissolve in and / or partially precipitate from such a liquid. Such behavior may still facilitate the separation of that element from others if its relative concentration in the liquid is different from its relative concentration in the solid. For instance, in some embodiments, an impurity metal dissolves in a liquid to a lesser extent than a rare-earth metal even though both the impurity metal and the rare-earth metal partially dissolve in the liquid. As another example, in some embodiments, an impurity metal precipitates from a liquid to a greater extent than a rare-earth metal even though both the impurity metal and the rare-earth metal partially precipitate from the liquid.

[0047] In some embodiments, subsequent to the feeding of a rare-earth metal-containing solid into a liquid, a liquid and a solid are recovered. The liquid may be enriched in one or more rare-earth metals of interest with respect to the rare-earth metal-containing solid and / or the solid may be enriched in one or more impurities (e.g., one or more impurity metals) in comparison to the rare-earth metal-containing solid. In some embodiments, a solid recovered after the feeding of a rare-earth metal-containing solid into a liquid comprises an impurity (e.g., an impurity metal, such as a transition metal, Ce, and / or La) that is present at a concentration that is greater than or equal to 150%, greater than or equal to 200%, greater than or equal to 500%, greater than or equal to 750%, greater than or equal to 1000%, greater than or equal to 2000%, greater than or equal to 5000%, or greater than or equal to 7500% (and, e.g., up to 10000%) of its concentration in the rare- earth metal-containing solid and / or is present in an even higher concentration.

[0048] The dissolution of a rare-earth metal in a liquid (e.g., from a solid material comprising the rare-earth metal) may be exothermic or endothermic. In some embodiments, the dissolution of the rare-earth metal into the liquid has an enthalpy of greater than or equal to -250 kJ / mol, greater than or equal to -200 kJ / mol, greater than or equal to -100 kJ / mol, greater than or equal to 0 kJ / mol, greater than or equal to 100 kJ / mol, greater than or equal to 200 kJ / mol, greater than or equal to 300 kJ / mol, greater than or equal to 400 kJ / mol, or greater than or equal to 500 kJ / mol. In some embodiments, the dissolution of the rare-earth metal into the liquid has an enthalpy of less than or equal to 550 kJ / mol, less than or equal to 500 kJ / mol, less than or equal to 400 kJ / mol, less than or equal to 300 kJ / mol, less than or equal to 200 kJ / mol, less than or equal to 100 kJ7mol, less than or equal to 0 kJ / mol, less than or equal to -100 kJ / mol, or less than or equal to -200 kJ / mol. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to -250 kJ / mol and less than or equal to 550 kJ / mol). Other ranges are also possible. The enthalpy of dissolution may be measured at 25 °C and 1 atm.

[0049] In some embodiments, dissolution of a rare-earth metal in a liquid results in the generation of one or more gases. Such gases may be formed by a reaction between one or more components of the solid material initially comprising the rare-earth metal and / or may result from the vaporization of the liquid into which the rare-earth metal is being dissolved (e.g., due to heat generated by the dissolution of the rare-earth metal therein). In some embodiments, one or more of the gases generated is acidic. It is also possible for CO2 gas, steam, and / or one or more organic gases to be generated.

[0050] In some embodiments, any gas generated by the dissolution of a rare-earth metal in a liquid (e.g., from a solid material comprising the rare-earth metal) is removed from the liquid relatively quickly. In some embodiments, at one hour after the dissolution of the rare-earth metal in the gas has been completed, less than 10 vol%, less than or equal to 7 vol%, less than or equal to 5 vol%, less than or equal to 2 vol%, less than or equal to 1 vol%, less than or equal to 0.75 vol%, less than or equal to 0.5 vol%, less than or equal to 0.2 vol%, less than or equal to 0.1 vol%, less than or equal to 0.075 vol%, less than or equal to 0.05 vol%, or less than or equal to 0.02 vol% of the gas generated by the dissolution is present in the form of gas bubbles positioned in the liquid. In some embodiments, at one hour after the dissolution of the rare-earth metal in the gas has been completed, greater than or equal to 0.01 vol%, greater than or equal to 0.02 vol%, greater than or equal to 0.05 vol%, greater than or equal to 0.075 vol%, greater than or equal to 0.1 vol%, greater than or equal to 0.2 vol%, greater than or equal to 0.5 vol%, greater than or equal to 0.75 vol%, greater than or equal to 1 vol%, greater than or equal to 2 vol%, greater than or equal to 5 vol%, or greater than or equal to 7.5 vol% of the gas generated by the dissolution is present in the form of gas bubbles positioned in the liquid. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.01 vol% and less than 10 vol%). Other ranges are also possible. In some embodiments, a reactor described herein is in fluidic communication with a gas scrubber and / or a method described herein comprises removal of a gas from a reactor and direction of the gas removed from the reactor to a gas scrubber. The gas scrubber may be capable of removing and / or configured to remove one or more hazardous components from gas passing therethrough. The gas scrubber may comprise a material (e.g., a basic material, such as dilute ammonia) that may react with one or more of the hazardous component(s) desired to be removed from the gas passing therethrough.

[0051] As noted above, some embodiments relate to mixing a liquid. The mixing may be performed in a variety of suitable manners. In some embodiments, mixing a liquid comprises stirring a liquid. The stirring may comprise rotating an impeller positioned in the liquid. In some embodiments, the impeller takes the form of a vertical blade mixer and / or is employed to perform radial flow mixing. In some embodiments, the impeller is formed of a corrosion-resistant material, such as a corrosion-resistant plastic.

[0052] An impeller may be rotated at a variety of suitable rates. In some embodiments, the impeller is rotated at a rate of greater than or equal to 100 rpm, greater than or equal to 200 rpm, greater than or equal to 500 rpm, greater than or equal to 750 rpm, greater than or equal to 1000 rpm, or greater than or equal to 2000 rpm. In some embodiments, the impeller is rotated at a rate of less than or equal to 5000 rpm, less than or equal to 2000 rpm, less than or equal to 1000 rpm, less than or equal to 750 rpm, less than or equal to 500 rpm, or less than or equal to 200 rpm. Combinations of the abovereferenced ranges are also possible (e.g., greater than or equal to 100 rpm and less than or equal to 5000 rpm). Other ranges are also possible.

[0053] In some embodiments, mixing a liquid may comprise forming a vortex therein. This may occur when the mixing causes a gas to be drawn into the liquid. When the liquid is stirred by an impeller, the vortex may form in the vicinity of the impeller and / or around the impeller. The vortex may comprise liquid that flows in an elliptical (e.g., a circular) and / or spiral manner. Such liquid may also flow in a direction parallel to the elliptical flow (e.g., the flow may comprise an elliptical component and / or spiral component and may, as a whole, form a helix).

[0054] In some embodiments, mixing a liquid causes the liquid to undergo turbulent flow. When the liquid is stirred by an impeller, the turbulent flow may occur in the vicinity of the impeller and / or around the impeller. Similarly, when a vortex is present, the turbulent flow may occur in the liquid forming the vortex, in the vicinity of the vortex, and / or around the vortex. Without wishing to be bound by any particular theory, it is believed that mixing a liquid such that it undergoes turbulent flow advantageously assists with reducing loss of material from the container containing the liquid. As discussed elsewhere herein, dissolution of a rare-earth metal in a liquid may cause the generation of bubbles and / or heat. Turbulent mixing may assist with dispersing these bubbles and / or heat throughout the liquid in a relatively rapid manner, which may reduce the formation of a froth that would overflow the container.

[0055] In some embodiments, the liquid is mixed such that it has a Reynolds number of greater than or equal to 1000, greater than or equal to 2000, greater than or equal to 3000, greater than or equal to 4000, greater than or equal to 5000, greater than or equal to 6000, greater than or equal to 7000, greater than or equal to 8000, greater than or equal to 9000, or greater than or equal to 10000. In some embodiments, the liquid is mixed such that it has a Reynolds number of less than or equal to 20000, less than or equal to 10000, less than or equal to 9000, less than or equal to 8000, less than or equal to 7000, less than or equal to 6000, less than or equal to 5000, less than or equal to 4000, less than or equal to 3000, or less than or equal to 2000. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1000 and less than or equal to 20000). Other ranges are also possible.

[0056] In some embodiments, a liquid that is mixed has, overall, a Reynolds number in one or more of the above-referenced ranges. It is also possible for one or more portions of a liquid being mixed to independently have a Reynolds number in one or more of the above-referenced ranges. For instance, a portion of a liquid forming a vortex may have a Reynolds number in one or more of the above-referenced ranges and / or a portion of a liquid proximate an impeller being spun may have a Reynolds number in one or more of the above-referenced ranges.

[0057] The Reynolds number may be calculated as follows: where p is the density of the liquid; u is the flow speed; L is the characteristic linear dimension; p is the dynamic viscosity of the liquid; and v is the kinematic viscosity of the liquid. Density may be determined by measuring the mass of a known volume of liquid. The dynamic viscosity may be determined with a rotational viscometer at the temperature and pressure at which the mixing is being performed. The characteristic length may be determined by measuring the diameter of the impeller when an impeller is employed to perform the mixing. The kinematic velocity can be calculated by multiplying the radius of the mixing impeller by the rotational velocity when an impeller is employed to perform the mixing.

[0058] As noted above, mixing a liquid may cause it to undergo flow that has an elliptical and / or circular component. In such embodiments, the angular velocity of the liquid may have a variety of suitable values. In some embodiments, a liquid that is being mixed has an angular velocity of greater than or equal to 10 rad / s, greater than or equal to 20 rad / s, greater than or equal to 50 rad / s, greater than or equal to 75 rad / s, greater than or equal to 100 rad / s, greater than or equal to 150 rad / s, greater than or equal to 200 rad / s, greater than or equal to 250 rad / s, greater than or equal to 300 rad / s, greater than or equal to 350 rad / s, greater than or equal to 400 rad / s, or greater than or equal to 450 rad / s. In some embodiments, a liquid that is being mixed has an angular velocity of less than or equal to 500 rad / s, less than or equal to 450 rad / s, less than or equal to 400 rad / s, less than or equal to 350 rad / s, less than or equal to 300 rad / s, less than or equal to 250 rad / s, less than or equal to 200 rad / s, less than or equal to 100 rad / s, less than or equal to 75 rad / s, less than or equal to 50 rad / s, or less than or equal to 20 rad / s. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 rad / s and less than or equal to 500 rad / s). Other ranges are also possible.

[0059] In some embodiments, a liquid that is mixed has, overall, an angular velocity in one or more of the above-referenced ranges. It is also possible for one or more portions of a liquid being mixed to independently have an angular velocity in one or more of the above-referenced ranges. For instance, a portion of a liquid forming a vortex may have an angular velocity in one or more of the above-referenced ranges and / or a portion of a liquid proximate an impeller being spun may have an angular velocity in one or more of the above-referenced ranges.

[0060] Mixing may be performed for a variety of suitable times. In some embodiments, a liquid is mixed for a period of time (e.g., subsequent to a step in which a rare-earth metal-containing solid material is fed into a liquid) of greater than or equal to 30 minutes, greater than or equal to 1 hour, greater than or equal to 1.5 hours, greater than or equal to 2 hours, greater than or equal to 2.5 hours, greater than or equal to 3 hours, or greater than or equal to 3.5 hours. In some embodiments, a liquid is mixed for a period of time (e.g., subsequent to a step in which a rare-earth metal-containing solid material is fed into a liquid) of less than or equal to 4 hours, less than or equal to 3.5 hours, less than or equal to 3 hours, less than or equal to 2.5 hours, less than or equal to 2 hours, less than or equal to 1.5 hours, or less than or equal to 1 hour. Combinations of the abovereferenced ranges are also possible (e.g., greater than or equal to 30 minutes and less than or equal to 4 hours, or greater than or equal to 30 minutes and less than or equal to 2 hours). Other ranges are also possible.

[0061] A variety of suitable liquids may be employed in the methods described herein. For instance, in some embodiments, an aqueous fluid is employed in a method described herein. As another example, in some embodiments, a liquid comprises an alcohol (e.g., methanol, ethanol).

[0062] In some embodiments, an aqueous liquid having an acidic pH is employed in a method described herein. For instance, a rare-earth metal-containing solid may be fed into an aqueous liquid having an acidic pH. Such liquids may comprise water and an acid, non-limiting examples of which include mineral acids, such as HC1, H2SO4, and HNO3.

[0063] In some embodiments, a rare-earth metal-containing solid is fed into a liquid having a pH of greater than or equal to -2, greater than or equal to -1.75, greater than or equal to -1.5, greater than or equal to -1.25, greater than or equal to -1, greater than or equal to -0.75, greater than or equal to -0.5, greater than or equal to -0.25, greater than or equal to 0, greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 0.75, greater than or equal to 1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.25, greater than or equal to 2.5, greater than or equal to 2.75, greater than or equal to 3, greater than or equal to 3.25, greater than or equal to 3.5, or greater than or equal to 3.75. In some embodiments, a rare-earth metal-containing solid is fed into a liquid having a pH of less than or equal to 4, less than or equal to 3.75, less than or equal to 3.5, less than or equal to 3.25, less than or equal to 3, less than or equal to 2.75, less than or equal to 2.5, less than or equal to 2.25, less than or equal to 2, less than or equal to 1.75, less than or equal to 1.5, less than or equal to 1.25, less than or equal to 1, less than or equal to 0.75, less than or equal to 0.5, less than or equal to 0.25, less than or equal to 0, less than or equal to -0.25, less than or equal to -0.5, less than or equal to -0.75, less than or equal to - 1, less than or equal to -1.25, less than or equal to -1.5, or less than or equal to -1.75. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to -2 and less than or equal to 4). Other ranges are also possible.

[0064] In some embodiments, the pH of an aqueous liquid into which a rare-earth metalcontaining solid is fed is selected such that, at the end of the feeding of the rare-earth metal-containing solid thereinto, the pH of the aqueous liquid is anticipated to be at a target value. The pH of the aqueous liquid appropriate to achieve a particular target value at the end of the above-described feeding may depend on the water content of the rare-earth metal-containing solid and its chemical composition (e.g., the amount and basicity of various components therein). Without wishing to be bound by any particular theory, it is believed that rare-earth metal-containing carbonates, oxides, and hydroxides may be basic, and so may raise the pH of aqueous liquids into which they are fed. Aqueous liquids into which rare-earth metal-containing solids are fed may accordingly initially have lower values of pH than such target values.

[0065] In some embodiments, the target value described in the preceding paragraph is greater than or equal to 1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.25, greater than or equal to 2.5, greater than or equal to 2.75, greater than or equal to 3, greater than or equal to 3.25, greater than or equal to 3.5, or greater than or equal to 3.75. In some embodiments, the target value described in the preceding paragraph is less than or equal to 4, less than or equal to 3.75, less than or equal to 3.5, less than or equal to 3.25, less than or equal to 3, less than or equal to 2.75, less than or equal to 2.5, less than or equal to 2.25, less than or equal to 2, less than or equal to 1.75, less than or equal to 1.5, or less than or equal to 1.25. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 4). Other ranges are also possible.

[0066] The containers described herein may comprise and / or take the form of a variety of suitable vessels. In some embodiments, a container comprises and / or takes the form of an acid-resistant vessel, such as a glass vessel and / or a polymeric vessel. In some embodiments, a container comprises and / or takes the form of an acid-resistant vessel (e.g., a glass vessel, a vessel formed from, comprising, consisting essentially of, and / or consisting of an acid-resistant polymer) comprising an acid-resultant cap (e.g., a cap formed from, comprising, consisting essentially of, and / or consisting of an acid-resistant polymer). In such embodiments, the cap may comprise one or more ports through which one or more species can be introduced into the vessel (e.g., through which a solid material comprising a rare-earth metal can be introduced thereinto, through which a gas can be introduced thereinto, through which a liquid can be introduced thereinto) and / or one or more ports through which one or more species can be removed from the vessel (e.g., through which a gas can be removed therefrom).

[0067] As noted above, in some embodiments, one or more method steps are performed while a gaseous atmosphere having a relatively low pressure is positioned above and in fluidic communication with a liquid in which a rare-earth metal is being dissolved. The relatively low pressure may be obtained and / or maintained in a variety of suitable manners. As one non-limiting example, in some embodiments, the relatively low pressure is obtained and / or maintained by having the gaseous atmosphere be in fluidic communication with a vacuum. The vacuum may comprise a pump and / or a reservoir held at a reduced pressure. The fluidic communication may be facilitated by tubing, such as tubing comprising, coated with, and / or consisting of a corrosion-resistant material (e.g., a corrosion-resistant plastic).

[0068] In some embodiments, the gaseous atmosphere has a pressure of less than or equal to 1 atm absolute, less than 1 atm absolute, less than or equal to 400 in H2O absolute, less than or equal to 390 in H2O absolute, less than or equal to 380 in H2O absolute, less than or equal to 370 in H2O absolute, less than or equal to 360 in H2O absolute, less than or equal to 350 in H2O absolute, less than or equal to 340 in H2O absolute, less than or equal to 330 in H2O absolute, less than or equal to 320 in H2O absolute, less than or equal to 310 in H2O absolute. In some embodiments, the gaseous atmosphere has a pressure of greater than or equal to 307 in H2O absolute, greater than or equal to 310 in H2O absolute, greater than or equal to 320 in H2O absolute, greater than or equal to 330 in H2O absolute, greater than or equal to 340 in H2O absolute, greater than or equal to 350 in H2O absolute, greater than or equal to 360 in H2O absolute, greater than or equal to 370 in H2O absolute, greater than or equal to 380 in H2O absolute, greater than or equal to 390 in H2O absolute, or greater than or equal to 400 in H2O absolute. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 1 atm and greater than or equal to 307 in H2O absolute). Other ranges are also possible.

[0069] The gaseous atmospheres described herein may comprise a variety of suitable gases, such as air and / or gases generated during the dissolution of a solid material into a liquid. One example of the latter type of gas is carbon dioxide (which may be generated when carbonates are dissolved into aqueous liquids).

[0070] In some embodiments, one or more further steps may be performed subsequent to the feeding of a solid comprising a rare-earth metal into a liquid. As noted above, one example of such a step is mixing the liquid. Non-limiting further examples of such steps include transferring the liquid to a second, different container (e.g., prior to and / or subsequent to any of the other further steps in this list), performing pH adjustment to bring the pH of the liquid to a target value (e.g., a target value described elsewhere herein), performing vacuum filtration, and performing one or more techniques to identify the composition of the liquid and / or any undissolved solids and / or precipitates. Performing pH adjustment may comprise adding an acid (e.g., one or more of the acids described elsewhere herein as being suitable for initially being present in the liquid) and / or a base (e.g., NaOH) to the liquid. Vacuum filtration may separate the liquid from any undissolved solids and / or precipitates associated therewith (e.g., suspended therein). The composition of a liquid may be determined via ICP-OES. The composition of a solid may be determined via SEM.

[0071] EXAMPLE 1

[0072] This Example describes a method of feeding a solid comprising a rare-earth metal into a liquid.

[0073] A pilot-scale dissolution of a rare-earth metal-containing solid into a liquid was performed in the container shown in FIG. 5. This container was a 100 L vessel that included three ports: one for feeding the rare-earth metal containing solid, one for removing gas from the container, and one through which a mixer extended.

[0074] First, the liquid was prepared and then introduced into the container. The liquid was an acidic aqueous liquid comprising HC1 and having a pH selected such that the target value of the pH of the liquid after dissolution of the rare-earth metal-containing solid thereinto was between 2.5 and 3.

[0075] Next, the rare-earth metal-containing solid was weighed and then fed into the liquid over the course of two hours and while the pressure in the container was held at less than 1 atm absolute. This solid was a carbonate comprising various rare-earth metals and impurities and including 36 wt% water. The concentrations of various components thereof are shown below in Table 1. This solid reacted vigorously with the liquid during the feeding process. Table 1.

[0076] After the rare-earth metal-containing solid was fully fed into the liquid, the mixer was employed to mix the liquid at 120 rpm for 30-60 minutes.

[0077] Finally, the liquid contained in the container was transferred to a second, different container for further processing. This further processing began with performing pH adjustment on the liquid, then subjecting the liquid to vacuum filtration, and finally performing ICP-OES on the resultant liquor and SEM on the filter cake.

[0078] Table 2, below, shows the amounts of various species in the filter cake. Table 3, below, shows the amounts of various species in the liquor. Table 2.

[0079] Table 3. While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0080] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0081] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0082] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0083] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

[0084] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. A method of dissolving a rare-earth metal in a liquid, comprising: feeding a solid material comprising the rare-earth metal into the liquid, wherein: the liquid is contained in a container, the container further contains a gaseous atmosphere positioned above and in fluidic communication with the liquid, a pressure of the gaseous atmosphere is less than or equal to 1 atm absolute, and the solid material is fed at a rate of greater than or equal to 0.1 g / min and less than or equal to 500 tons / min.

2. A method of dissolving a rare-earth metal in a liquid, comprising: feeding a solid material comprising the rare-earth metal into the liquid, wherein: the liquid is contained in a container, the container is enclosed in a reactor further comprising a gaseous atmosphere positioned above and in fluidic communication with the liquid, a pressure of the gaseous atmosphere is less than or equal to 1 atm absolute, and the solid material is fed at a rate of greater than or equal to 0.1 g / min and less than or equal to 500 tons / min.

3. The method of claim 1 or claim 2, wherein the dissolution of the rare-earth metal in the liquid is exothermic.

4. The method of any preceding claim, wherein the dissolution of the rare-earth metal in the liquid is endothermic.

5. The method of any preceding claim, wherein the enthalpy of the dissolution of the rare-earth metal in the liquid is greater than or equal to -250 kJ / mol and less than or equal to 550 kJ / mol.

6. The method of any preceding claim, wherein, at one hour after the dissolution of the rare-earth metal in the liquid has been completed, less than 10 vol% of the gas generated by the dissolution is present in the form of gas bubbles positioned in the liquid.

7. The method of any preceding claim, wherein the gaseous atmosphere is in fluidic communication with a vacuum.

8. The method of any preceding claim, wherein the solid material further comprises an impurity metal.

9. The method of any preceding claim, wherein the solid material further comprises two or more impurity metals.

10. The method of any preceding claim, wherein the impurity metal(s) comprise aluminum and / or cerium.

11. The method of any preceding claim, further comprising dissolving the impurity metal in the liquid.

12. The method of any preceding claim, further comprising precipitating the impurity metal from the liquid.

13. The method of any preceding claim, wherein the impurity metal does not fully dissolve in the liquid.

14. The method of any preceding claim, wherein the impurity metal dissolves in the liquid to a lesser extent than the rare-earth metal.

15. The method of any preceding claim, further comprising mixing the liquid.

16. The method of any preceding claim, wherein the mixing is performed with an impeller.- 1 -17. The method of any preceding claim, wherein the impeller is a vertical-blade impeller.

18. The method of any preceding claim, wherein the impeller is rotated at a rate of greater than or equal to 100 rpm and less than or equal to 5000 rpm.

19. The method of any preceding claim, wherein the liquid has a Reynolds number of greater than or equal to 1000 and less than or equal to 20000.

20. The method of any preceding claim, wherein the mixing causes the formation of a vortex.

21. The method of any preceding claim, wherein the dissolution of the rare-earth metal in the liquid generates acid gases.

22. The method of any preceding claim, wherein the reactor is in fluidic communication with a gas scrubber.

23. The method of any preceding claim, wherein the feeding is performed with the use of a hopper and / or a feeder.

24. The method of any preceding claim, wherein the rare-earth metal does not fully dissolve in the liquid.

25. The method of any preceding claim, further comprising precipitating the rare- earth metal from the liquid.

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