Rare Earth Elements, Hydrides and Mutual Alloys


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Element System

In the following, further exemplary embodiments of the method will be explained. As additive, sodium sulphate Na 2 SO 4 may be used as an aqueous solution. Furthermore, it is possible to use the corresponding solid materials as an alternative to an aqueous solution. The two sub-steps of precipitation adding sulphates to the solution of the solubilized metals, and adding an alkaline solution to the solution of the solubilized metals for increasing the ph-value may be performed sequentially i.

In an embodiment, the acidic leaching is performed in a halogen acid solution preferably in a hydrochloric acid solution. The halogen acid may be the only acid component in the solution. Alternatively, a phosphoric acid is suitable for acidic leaching.

Rare Earth Elements, Hydrides and Mutual Alloys

However, other acids may be used as well provided that the valuable materials including the rare earth metals are brought to a sufficient degree, preferably completely, in solution, whereas at the same time non-metallic residue materials such as plastic or graphite remain in a solid phase and can therefore be separated.

In an embodiment, the acidic leaching is performed at a pH-value of less than about 3, particularly in a range of ph-values between about 0 and about The disclosed ranges of ph-values particularly ensure that all rare earth metals which are to be recycled as well as a large amount of other metals are completely dissolved from the solid phase into a liquid phase. The ph-value is a measure of the acidity or basicity of a solution.

A low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration.


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  • USA - Gastight, sealed metal oxide/metal hydride storage battery - Google Patents.
  • Journal of Alloys and Compounds (v.350, #1-2)!

The pH-value as used herein is not precisely p[H] i. This represents the tendency of hydrogen ions to interact with other components of the solution, which affects among other things the electrical potential read using a pH-meter. As a result, pH can be affected by the ionic strength of a solution. In order to obtain a dissolution of the metals included in the waste material, a very small pH-value is advantageous.

More generally, all rare earth metal comprising residue materials can be used as waste material to be recycled according to exemplary embodiments of the invention. This predominantly includes nickel metal hydride batteries, but also special alloys, magnetic members based on the 4f magnetism of the rare earth metals, high temperature fuel cells or luminescent material in lamps.

Zeitschrift für Naturforschung B

The term "nickel metal hydride battery" or nickel-metal hydride cell, abbreviated NiMH, may particularly denote a type of secondary electrochemical cell similar to a nickelcadmium cell. The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. The positive electrode is nickel oxyhydroxide NiOOH. In an embodiment, adding the sulphates to the solution is performed prior to adding the alkaline solution to the solution.

In an alternative embodiment, adding the alkaline solution to the solution is performed prior to adding the sulphates to the solution.

Journal of Alloys and Compounds (v, #) | bumcsisthkgoogla.tk

It is also possible that both additions are performed at the same time, for instance as a common solution. In an embodiment, the precipitating comprises rising the ph-value in the solution of the solubilized metals. Increasing the pH-value to a certain value can therefore be achieved by adding a basic solution to the acidic solution of the solubilized metals.

By properly adjusting the alkaline solution in its chemical properties, it is possible to selectively control which materials are converted into the solid phase.


  1. Functional analysis, holomorphy, and approximation theory II: proceedings of the Seminario de Analise Funcional, Holomorfia e Teoria da Aproximacao, Universidade Federal do Rio de Janeiro, August 3-7, 1981;
  2. Rare Earth Elements, Hydrides and Mutual Alloys;
  3. US5639569A - Gastight, sealed metal oxide/metal hydride storage battery - Google Patents.
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  8. In a preferred embodiment, the ph-value is increased to such a value that selectively only the rare earth metals are converted into the solid phase. The precipitation may comprise any treatment of the solution in such a way that the rare earth metals precipitate as a solid. This may be achieved by partially or completely neutralizing the solution which has been brought into the acid range by the acidic leaching process.

    For instance, the precipitating may comprise rising the ph-value to a range between 0 and 4, particularly to a range between 1,5 and 2,5. Other ph-values are possible as well. In an embodiment, the precipitating comprises adding an alkaline solution to the solution of the solubilized metals. However, other alkaline solutions are possible as well. The sulphates may promote the formation of solid compounds comprising rare earths, since rare earth sulphates are not easily dissolvable and thereby remain sufficiently stably in the solid phase.

    In an advantageous embodiment, the acidic leaching solution comprises or consists of an aqueous solution of hydrochloric acid and the alkaline solution comprises or consists of a sodium hydroxide solution wherein sulphates may be added thereto. Without wishing to be bound to a specific theory, it is presently believed that the use of a hydrochloric acid for acidic leaching and a sodium hydroxide solution including sulphate for subsequent precipitation results in a high yield of rare earth metal compounds being precipitated. The former ensures that a very large percentage of the metals preferably also including nickel are dissolved, the latter ensures an almost complete subsequent precipitation of the rare earth metal compounds.

    In an embodiment, the precipitating comprises adding sulphates for precipitating sulphates of the rare earth metals. Additionally, sodium can be partly or completely replaced by potassium. Particularly in an embodiment in which hydrochloric acid is used for the acidic leaching, the addition of sulphates can be used for further increasing the yield of rare earth metal material being in fact precipitated during the precipitating process.

    The addition of sulphates results in the formation of rare earth sulphate compounds which are not prove to be dissolved again. In an embodiment, the leaching comprises adding hydrogen peroxide for promoting dissolution of nickel. This embodiment is particularly advantageous when a complete dissolution of all metals is desired, since the addition of hydrogen peroxide further increases the yield of such metals particularly nickel which is brought in solution. In an embodiment, the method further comprises separating the precipitated rare earth metals from a remaining solution, after the precipitation.

    Hence, it is also possible that other valuable materials are recycled by exemplary embodiments of the invention. In an embodiment, any of the separating steps i. Filtration is an appropriate method, since it can reliably separate different components with reasonable expenditure. In an embodiment, the method further comprises comminuting the waste material before the acidic leaching, particularly by grinding, shearing or shredding. For instance, a used nickel metal hydride battery can be comminuted by cutting it into pieces.

    National Minerals Information Center

    An electrode packet may be comminuted by opening the casing in order to increase the active surface on which the acidic leaching solution may attack the components of the waste material. The comminuted waste material may be directly inserted into the leaching solution without any need for smelting or the like. In an embodiment, the method further comprises, after having precipitated the rare earth metals, recovering for instance precipitating selectively at least one further of the valuable materials, particularly at least one of nickel and cobalt, in the solution while maintaining other metals in dissolved form.

    Such a precipitation may be performed in a similar way as the precipitation of the rare earth metals, i. As an alternative to the recovery of the further valuable materials by selectively precipitating, it is also possible to recover them by other methods such as electrolysis. In an embodiment, the method further comprises, after having precipitated the rare earth metals, recirculation of at least a part of liquids used during executing the method for a next charge of waste material for recycling rare earth metals therein.

    By taking this measure, the waste liquid to be disposed may be reduced to a minimum. The used solution may be purified to be used again. In an embodiment, the entire recycling method is purely hydrometallurgic. The term "hydrometallurgical" may particularly denote a part of the field of extractive metallurgy involving the use of aqueous chemistry for the recovery of metals from ores, concentrates, and recycled or residual materials. Hydrometallurgy is typically divided into three general areas, i.

    In other words, the entire recycling method may be free of any pyrolysis treatment of the waste material.

    go here Alternatively, a pyrometallurgic process may be added only after the separation of the rare earth materials by precipitation. For instance, a calcination process may be added at the end of such a recycling procedure. However, the optionally comminuted waste material may be directly placed in an acidic leach without prior pyrolysis. Solid components in the leaching solution may comprise pyrolysable material such as organic substances, plastic, polymers.

    In an embodiment, the acidic leaching of the waste material may be performed by using a leaching solution consisting of a non-oxidizing acid, i. Alternatively, the leaching solution comprising the non-oxidizing acid may optionally comprise one or more additives, for example a contribution of an oxidizing acid. It is also possible that the leaching solution comprises a mixture of two or more different non-oxidizing acids. In an embodiment, the sulphates are added to the solution of the solubilized metals only for precipitation, i.

    It is however also possible that sulphates are added to the solution already for leaching. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited:. The illustrations in the drawings are schematically. In different drawings similar or identical elements are provided with the same reference signs. In an exemplary embodiment, rare earth metals are recycled from nickel metal hydride batteries.

    However, most existing industrial recycling processes extract basically nickel as a pure metal or in the form of alloys, whereas the rare earths are lost in pyrometallurgic slag. The recycling method according to an embodiment of the invention focuses on the additional recycling of the rare earth metals apart from other valuable metals nickel, cobalt, etc. The disclosed process approach comprises a sufficient crushing or disintegration or grinding of the battery cells and the subsequent leaching in highly acidic solutions. After a filtration of the unsoluble residue, an increase of the pH-value results in a selective precipitation of compounds which preferably comprise elements of the rare earths.

    Goal of such a process is a complete dissolution of the metallic components of the NiMH cells and on the other hand to obtain a yield as high as possible when precipitating the rare earth metals with a sufficiently low degree of impurities. In the following, referring to Fig. In a block , the batteries are grinded into small particles thereby simplifying a subsequent acid attack on materials of these particles due to an increase of the surface.

    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys
    Rare Earth Elements, Hydrides and Mutual Alloys Rare Earth Elements, Hydrides and Mutual Alloys

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