JP2013053365A - Method for manufacturing metallic particle utilizing solvothermal reaction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture metallic particles efficiently by a solvothermal reaction from a mixed solution including a plurality of metallic ions.SOLUTION: A method uses a mixed solution including ions of metal (a) and ions of metal (b) that is different from the metal (a). In the method, metallic particles (A) of the metal (a) are produced by reducing ions of the metal (a) by a following process (1) or a process (2). The process (1) includes steps of: separating ions of the metal (a) from the mixed solution; converting the metal (a) to a metal hydroxide; subjecting the metal hydroxide to solvothermal reaction under the presence of an organic solvent (C1) that can reduce ions of the metal (a); and producing the metallic particles (A). The process (2) includes steps of: subjecting the mixed solution to a solvothermal reaction under the presence of an organic solvent (C2) that can reduce ions of the metal (a) and does not reduce ions of the metal (b); and producing the metallic particles (A).

Description

  The present invention relates to a method for efficiently producing metal particles by a solvothermal reaction from a mixed solution containing a plurality of metal ions (for example, a waste solution such as a plating waste solution).

  For example, mine wastewater, chemical factory wastewater, smelter wastewater, ironworks wastewater, plating factory wastewater, waste incinerator wastewater, and acidic aqueous solutions extracted from recycled products such as home appliances are used as waste liquids (metal wastewater) in which metal ions are dissolved. is there.

  Such wastewater contains metal ions such as vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, ruthenium, rhodium, palladium, silver, tungsten, rhenium, iridium, platinum, and gold. Yes. In order to recover metal ions from such wastewater as valuable resources and recycle them, selective separation and decomposition (separation) technology for separating metal ions and selectively separated metal ions are used. It is necessary to have a technology for recycling dissolved ions for recycling.

  Separation techniques for selectively separating metal ions include solvent extraction techniques, precipitation techniques, adsorption techniques, microorganism-based techniques, and refining techniques. Is becoming possible.

  Following the selective separation of metal ions, as a technique for recycling metal ions dissolved in an aqueous solution, an electrolytic collection technique, an insolubilization technique, a refining technique, and a technique using a hydrothermal reaction have been developed. However, with the conventional recycling technology, dissolved metal ions cannot be recycled economically, and recovery and reuse of valuable metals from wastewater are often not advanced to a practical level.

  For example, in the method described in Japanese Patent No. 2997110 (Patent Document 1), high-purity copper is deposited on the cathode by the electrolytic collection method, so that valuable metals can be recovered and reused, but the anode is placed in a tank in which metal ions are dissolved. Therefore, enormous electric energy is required, the cost is not met, and it is not practical as a valuable metal recovery method.

  Further, in the methods described in Japanese Patent No. 4388091 (Patent Document 2) and Japanese Patent No. 4440761 (Patent Document 3), although dissolved metal ions can be recovered as a metal salt, the dissolved metal species As the number increases, the type of drug used and the solid-liquid separation process become more complicated, and there is a problem that the process becomes complicated and the cost becomes high. Moreover, since the utility value is low in the state of metal salt and it is cheaper to use a new product than to use a recovered product, it is difficult to establish a recycling technology.

  In addition, techniques for refining dissolved metal ions recovered by insolubilization and sludge recycling have been studied for a long time, but since dry refining is performed, there is a problem that the cost similarly increases.

  In recent years, hydrothermal reactions and hydrothermal mineralization methods are known as newly developed methods for recycling dissolved metal ions. For example, in Japanese Patent No. 4064850 (Patent Document 4), a reaction in a high temperature and high pressure aqueous medium, that is, a hydrothermal reaction (also referred to as hydrothermal synthesis), zirconium, molybdenum, iron, chromium, palladium or It is described that copper can be recovered as each oxide and can be recycled. Hydrothermal mineralization is a technology that mimics the principle of mineral production performed in the earth's crust. Non-patent document 1 (Chemical Industry, July 2008, pages 45 to 51) includes a mineralizer. It is described that chromium, phosphorus, arsenic, boron, fluorine and the like can be recovered by heating metal ions at high temperature and high pressure.

  However, in the recycling of metal ions by such a hydrothermal reaction, the compounds obtained by recycling are limited to metal oxides due to the oxidizing power of water. Further, when the generated metal oxide becomes nanometer-sized particles (called nanoparticles), there is a feature that aggregation is likely to occur due to the high surface energy of the nanoparticles.

  As described above, the dissolved metal ions in the waste liquid are not reused and are sludged and disposed of because of process efficiency and economical reasons. There is a need for a technology that can recover and reuse valuable metals and harmful metals that can be recycled and applied efficiently to nanoparticles other than metal oxides.

  In recent years, solvothermal reactions using various organic solvents have attracted attention. The feature of this solvothermal reaction is that, unlike an aqueous medium, the reaction is performed in a reducing atmosphere by using an organic solvent, so that the obtained particles are not limited to metal oxides. . Another feature is that the compound to be produced is likely to be nanoparticles, and there is an organic substance derived from the organic solvent used on the surface, and the advantage that the produced nanoparticles can be dispersed in the solvent relatively easily. Have. Furthermore, since nanoparticles can be synthesized from a uniform liquid phase by coexisting a surfactant during reaction preparation, the dispersibility of the produced nanoparticles in a solvent can be enhanced. As a prior art using such a solvothermal reaction, in JP 2009-233845 A (Patent Document 5), a surfactant is added to a solvent such as ethanol or N, N-dimethylformamide (DMF). It is described that metal nanoparticles and metal oxide nanoparticles can be synthesized from a homogeneous liquid phase without agglomeration. In the method of this document, nanoparticles having a size of several nanometers to several tens of nanometers are obtained in an isolated and dispersed state.

  In this document, in addition to nanoparticles composed of simple metals, metal oxide nanoparticles including a plurality of metals are also assumed, but a plurality of metals can be generated in the form of separate particles. Therefore, a plurality of metals cannot be separated.

Japanese Patent No. 2997110 (Claims) Japanese Patent No. 4388091 (Claims) Japanese Patent No. 4440761 (Claims) Japanese Patent No. 4064850 (Claims) JP2009-233845A (Claims, Examples)

Chemical Industry July 2008, pages 45-51

  Accordingly, an object of the present invention is to provide a method for efficiently producing metal particles from a mixed solution containing a plurality of metal ions by a solvothermal reaction.

  Another object of the present invention is to provide a method capable of efficiently separating each metal ion as separate particles from a mixed solution containing a plurality of metal ions.

  The inventors of the present invention have either (i) separated a desired metal ion as a specific metal compound (ie, metal hydroxide) and subjected to a solvothermal reaction, or (ii) ) By subjecting to a solvothermal reaction in the presence of a specific organic solvent (for example, alcohols) capable of reducing the desired metal ion, the desired metal ion is mixed in the form of metal particles (metal single particles, etc.). In the latter method (ii), a plurality of metal ions are separated from particles of desired metal ions (such as single metal particles) (for example, metal oxide particles). In addition to the desired metal ions, other metal ions can be easily separated and recovered, and in both methods (i) and (ii) In order to utilize thermal reaction, the surface of the desired metal ion is coated with an organic layer derived from the organic solvent or surfactant (amines, etc.) used in the reaction, and stabilized metal particles (particularly metal nanoparticles). The present invention has been completed.

That is, in the method of the present invention, the following step (1) or (2) is performed using a mixed liquid containing ions of the metal (a) and ions of the metal (a) and a metal (b) having a different metal species. Then, the metal (a) ions are reduced to produce metal (a) metal particles (A).
(1) After separating ions of metal (a) from the mixed liquid and converting them into metal hydroxides of metal (a), in the presence of an organic solvent (C1) capable of reducing the ions of metal (a), Step (2) in which the metal hydroxide is subjected to a solvothermal reaction to produce metal particles (A), the mixture can reduce the ions of the metal (a) and does not reduce the ions of the metal (b) A step of generating metal particles (A) by subjecting to a solvothermal reaction in the presence of an organic solvent (C2).

  In the above method, the ionization tendency of the metal (b) may be larger than the ionization tendency of the metal (a). Further, the difference between the standard oxidation-reduction potential (25 ° C.) of the metal (a) and the standard oxidation-reduction potential (25 ° C.) of the metal (b) may be 0.2 V or more, for example.

  In the above method, typically, the metal (a) is at least one selected from Group 8 metal of the periodic table, Group 9 metal of the periodic table, Group 10 metal of the periodic table, Group 11 metal of the periodic table. And the metal (b) is a periodic table group 4 metal, a periodic table group 5 metal, a periodic table group 6 metal, a periodic table group 7 metal, a periodic table group 8 metal, a periodic table group 12 metal, and It may be at least one selected from Group 13 metals of the periodic table. In particular, the metal (a) is at least one selected from cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, and gold, and the metal (b) is titanium, zirconium, manganese, zinc. In addition, at least one selected from gallium and indium may be included.

  In the present invention, when the metal (a) contains a plurality of metals, alloy particles containing these metals can also be produced as the metal particles (A). Therefore, in the method, the metal (a) contains a plurality of metals, and the metal particles (A) include alloy particles containing these metals (for example, nickel-cobalt alloy particles, alloy particles made of a plurality of noble metals, etc.) ) May be generated.

  The mixed liquid may be a waste liquid, for example, a plating waste liquid.

  In the step (1), the ions of the metal (a) may be separated by extracting and separating the ions of the metal (b) from the mixed solution. For example, in step (1), the metal (b) ions are separated from the mixture using an extractant that does not extract the metal (a) ions and can extract the metal (b) ions. Also good.

  In particular, in the step (1), the metal (b) ions are separated, and the metal (a) ions are further separated by extraction from the separation liquid containing the metal (a) ions and converted into metal hydroxides. May be. For example, in step (1), metal (a) ions are separated using an extractant, and metal (a) ions are extracted from the extractant containing metal (a) ions by back extraction with an acid component. You may isolate | separate with the form of the acidic solvent containing the ion of a metal (a), and you may convert into a metal hydroxide.

  In the method (step (1) or step (2)), the organic solvent (C1) or (C2) may be an alcohol, particularly a glycol (particularly 1,4-butanediol).

  In the method (step (1) or step (2)), a solvothermal reaction may be further performed in the presence of a surfactant (for example, amines).

  The metal particles (A) obtained by the above method may usually be nanoparticles. Typically, the metal particles (A) are formed of core particles composed of the metal (a) and components derived from the organic solvent (C1) or (C2) (and surfactant) on the surface of the core particles. Nanoparticles including the formed organic layer may be used.

  In the step (2), metal particles (B) (for example, metal oxide particles) of the metal (b) are generated together with the metal particles (A) (for example, simple metal particles and alloy particles) by a solvothermal reaction. You may let them.

  In the present specification, “metal ion” means that the metal has an ion binding property (or a value with an oxidation number exceeding 0), and is not only present in the mixed solution as an ion (cation). In some cases, an ionic bond is formed in a metal salt or metal compound without being dissolved (ionized).

  In the present invention, metal particles can be efficiently produced (separated or recovered) by a solvothermal reaction from a mixed solution containing a plurality of metal ions through a specific process. That is, according to the method of the present invention, since a solvothermal reaction can be used, a desired metal ion is stabilized from a mixture liquid (mixed system) containing a plurality of metal ions so that aggregation or the like hardly occurs. It can be separated as metal particles (metal nanoparticles). Further, in the method of the present invention, each metal ion is not treated as a particle (eg, composite metal oxide particle) from a mixed solution containing a plurality of metal ions, but as separate particles (for example, It can be separated efficiently (divided into single metal particles, alloy particles, and metal oxide particles). Therefore, particles (particularly nanoparticles) of each metal can be easily separated and collected by a method such as applying magnetism.

  In the method of the present invention, a mixed solution containing ions of the metal (a) and ions of the metal (a) and a metal (b) having a different metal species is used, and after a specific step (1) or (2). The metal (a) ions are reduced to produce metal particles (A) of metal (a) (particles containing metal (a) as a metal component).

[Mixture]
The mixed solution contains ions of metal (a) and ions of metal (b). The metal (a) and the metal (b) are not particularly limited as long as they can be separated, and depending on the step (1) and the step (2), for example, a Group 2 metal of the periodic table (for example, magnesium), Periodic table group 3 metals (eg, scandium, yttrium, lanthanoids, etc.), periodic table group 4 metals (eg, titanium, zirconium, etc.), periodic table group 5 metals (eg, vanadium, niobium, tantalum, etc.), periodicity Table Group 6 metals (eg, chromium, molybdenum, tungsten, etc.), Periodic Table Group 7 metals (eg, manganese, etc.), Periodic Table Group 8 metals (eg, iron, ruthenium, osmium, etc.), Periodic Table No. 9 Group metals (eg, cobalt, rhodium, iridium, etc.), Periodic Table Group 10 metals (eg, nickel, palladium, platinum), Periodic Table Group 11 metals (eg, Copper, silver, gold), periodic table group 12 metals (eg, zinc, cadmium, mercury), periodic table group 13 metals (eg, aluminum, gallium, indium, etc.), periodic table group 14 metals (eg, germanium) , Tin, lead, etc.), periodic table group 15 metals (for example, antimony, bismuth, etc.). The metal (a) and the metal (b) may be used alone or in combination of two or more. As long as the metal (a) and the metal (b) are different from each other, they may be metals of the same group as long as they can be separated.

  In addition, the valence or oxidation number of ions (cations) can be appropriately selected according to the type of metal, and monovalent (+1), divalent (+2), trivalent (+3), tetravalent (+4), pentavalent. Any of (+5), hexavalent (+6) and the like may be used. For example, the valence of nickel ions is typically +2, +4, etc., and in particular may be +2. The valence of zinc ions may typically be +2.

  In particular, the metal (b) may be a metal larger than the metal (a) in the ionization tendency. In other words, the metal (b) (the ion of the metal (b)) is smaller in the standard oxidation-reduction potential (or standard electrode potential) than the metal (a) (the ion of the metal (a)). Ion). Such combinations of metal (a) and metal (b) are often easily separated from each other.

  The difference between the standard oxidation-reduction potential (25 ° C.) of the metal (a) (or its ion) and the standard oxidation-reduction potential (25 ° C.) of the metal (b) (or its ion) is, for example, 0.1 V or more ( For example, 0.15 to 4 V), preferably 0.2 V or more (for example, 0.25 to 3.5 V), more preferably 0.3 V or more (for example, 0.35 to 3 V), particularly 0.4 V or more ( For example, it may be 0.45 to 2.5 V).

  In addition, when a metal (a) contains a some metal, an alloy particle (or composite metal particle) can be obtained as mentioned later. In such a case, the difference between the standard redox potential (25 ° C.) of each metal (a) (or its ion) and the standard redox potential (25 ° C.) of the metal (b) (or its ion) is within the above range. May be satisfied.

  Moreover, although the difference of the standard oxidation-reduction potential (25 degreeC) between several metal (a) (or its ion) is based also on the standard oxidation-reduction potential (25 degreeC) of a metal (b) (or its ion), For example, 2 V or less (for example, 0.001 to 1.5 V), preferably 1 V or less (for example, 0.005 to 0.8 V), more preferably 0.5 V or less (for example, 0.01 to 0.4 V). In particular, it may be 0.3 V or less (for example, 0.015 to 0.3 V, preferably 0.015 to 0.2 V).

  The representative metal (a) includes at least one selected from Group 8 metal of the periodic table, Group 9 metal of the periodic table, Group 10 metal of the periodic table, Group 11 metal of the periodic table, and the like. In particular, the metal (a) may contain at least one selected from cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, and gold.

  Also, representative metals (b) include periodic table group 4 metal, periodic table group 5 metal, periodic table group 6 metal, periodic table group 7 metal, periodic table group 8 metal, periodic table group At least one selected from Group 12 metals and Group 13 metals of the periodic table is included. In particular, the metal (b) may contain at least one selected from titanium, zirconium, manganese, zinc, gallium and indium.

In addition, the mixed liquid may contain cations other than the ions of the metal (a) and the ions of the metal (b) [for example, hydrogen ions (H ⁺ ) and the like].

  In the mixed solution, the ratio of the metal (a) ions to the metal (b) ions is not particularly limited. For example, the former / the latter (weight ratio) = 99.9 / 0.1 / 1/99. , Preferably 99.5 / 0.5 to 5/95, more preferably about 99/1 to 10/90.

The mixed solution contains anions as ions of metal (a), ions of metal (b), and counter ions of other cations. Such anions are not particularly limited, and for example, halide ions (Cl ⁻ , Br ⁻ , I ⁻ etc.), inorganic acid ions [for example, sulfate ions (SO ₄ ²⁻ ), nitrate ions (NO ₃ ⁻ ) , Phosphate ion, hydrogen phosphate ion, dihydrogen phosphate ion, phosphite ion, hypophosphite ion, carbonate ion, bicarbonate ion, etc.], organic acid ion (eg acetate ion, citrate ion, etc.) Conjugated bases of diketone compounds (for example, acetylacetonate, etc.). The mixed solution may be used alone or in combination of two or more.

The solvent constituting the mixed solution is not particularly limited, and water, an organic solvent {for example, alcohols [for example, alkanol (for example, C _1-4 alkanol such as methanol, ethanol, propanol, isopropanol, butanol), polyhydric alcohol] (Eg, glycols such as ethylene glycol, propylene glycol and diethylene glycol, polyols such as glycerin), etc.], ketones (acetone, methyl ethyl ketone, cyclohexanone, etc.), amides (formamide, acetamide, N-methylformamide, N-methyl) Acetamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), ethers (dioxane, tetrahydrofuran, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.) , Cellosolve acetates (such as ethyl cellosolve acetate), carbitols (such as methyl carbitol, ethyl carbitol, butyl carbitol), carboxylic acids (such as acetic acid)} and the like. The solvents may be used alone or in combination of two or more.

  In particular, the mixed solution may contain water as a main component as a solvent component. In such a mixed solution (for example, an aqueous solution or an aqueous solution), the ratio of water to the whole solvent component is 50% by weight or more (for example, 60% by weight or more), preferably 70% by weight or more (for example, 75% by weight or more). ), More preferably 80% by weight or more (for example, 85% by weight or more), particularly 90% by weight or more (for example, 95% by weight or more).

  The mixed solution may be any of acidic, neutral, and alkaline (basic). Depending on the combination of the metal (a) and the metal (b), etc., the ions of the metal (b) in the step (1) It may be adjusted as appropriate when separating the solvent or during the solvothermal reaction. In particular, when the mixed solution is acidic, for example, the value of pH (25 ° C.) may be 1 to 6.5, preferably 2 to 6, and more preferably about 3 to 5.5. Examples of the acid constituting the acidic mixed solution include acids corresponding to the halide ions such as sulfuric acid, nitric acid and hydrogen halide, and inorganic acid ions.

  The mixed liquid may be a waste liquid (for example, plating waste liquid). The waste liquid contains various metal ions, acid components, solvents, and the like. In the present invention, even such a waste liquid can be efficiently separated and recovered, and can be recycled. In addition, when using a waste liquid (plating waste liquid etc.) as a liquid mixture, it is often acidic.

  In addition, when using a liquid mixture for a process (1) or a process (2), you may remove and use a part of solvent component by concentration etc. as needed.

[Step (1)]
In step (1), the presence of an organic solvent (C) capable of reducing the metal (a) ions after separating the metal (a) ions from the mixed solution and converting them into metal hydroxides of the metal (a). Below, the said metal hydroxide is used for a solvothermal reaction, and a metal particle (A) is produced | generated. Such step (1) differs from step (2) described later in that separation of ions of metal (a) is necessary, but metal particles (A) with high purity of metal (a) are surely obtained. Therefore, it is useful when the composition of the mixed solution is complicated or when it is difficult to select an appropriate organic solvent (C2) described later due to such a complicated composition. .

(Method for separating metal (a) ions)
The method for separating metal (a) ions from the mixture is not particularly limited, and methods such as extraction, adsorption, and neutralization can be used. Typically, the metal (b) ions may be separated from the mixed solution by extraction to obtain a separation solution containing the metal (a) ions.

  The extraction method of the ions of the metal (b) can be selected depending on the kind of the ions of the metal (b) or the combination with the ions of the metal (a). Usually, the extraction of the metal (a) ions (or adsorption) is performed. In addition, an extraction agent (sometimes referred to as an extraction agent B) capable of extracting (or adsorbing) ions of the metal (b) can be used.

  Such an extractant (or adsorbent) separates metal (b) ions from the mixed solution on the basis of a principle of selectively forming a complex with metal (b) ions (ion exchange). That is, by using such an extractant, it is possible to separate the metal (b) ions from the mixed solution by precipitating the ions together with the extractant or transferring them to a layer different from the metal (a) ions. For example, when the mixed solution is an aqueous solution, the extractant B and a non-aqueous solvent (hydrophobic solvent) are mixed with the mixed solution, whereby the layer containing the metal (a) ions (water layer) and the metal (b) ) And a non-aqueous solvent layer containing the extractant B.

  The extractant B is not particularly limited as long as the metal (a) and the metal (b) can be separated. For example, in the case of an extractant that forms a complex, a combination of the metal (a) and the metal (b). Accordingly, an extractant that is more easily complexed with the metal (b) than with the metal (a) can be selected.

  In addition, as extraction agent B in the case of extracting zinc ions etc. in the plating waste liquid, for example, phosphorus-based extraction agents [for example, “PC-88A” manufactured by Daihachi Chemical Industry Co., Ltd.] and the like can be used. .

  In the extraction, the mixed solution may be acidic, neutral, or alkaline. In particular, when the mixed solution is acidic, the pH (25 ° C.) of the mixed solution may be 2 to 6, preferably 3 to 5.5, more preferably about 3.5 to 5. The pH may be appropriately adjusted by adding an acid component or an alkali component to the mixed solution.

  Although the usage-amount of the extractant B is based also on a kind, it is 5000-500 weight part with respect to 1 weight part of ions of a metal (b), Preferably it is 2500-1000 weight part, More preferably, it is 2000-1500 weight. It may be about a part.

  In this manner, the metal (b) ions are separated from the mixed liquid, and a separation liquid containing the metal (a) ions is obtained. The separated metal (b) ions may be reused. For example, the metal (b) ions separated by the extractant B can be recovered by back extraction with an acidic solvent, as in the case of the metal (a) ions described below.

  The conversion of the metal (a) ions into the metal hydroxide may be performed in such a separation liquid, and further, the ions of the metal (a) may be separated from the separation liquid. Since the separation liquid usually contains ions other than the metal (a) ion, the purity of the metal (a) is increased, and the conversion to metal hydroxide and the solvothermal reaction described later are performed efficiently. Further, it is preferable to separate the metal (a) ions from the separation liquid.

  The method for separating the metal (a) ions from the separation liquid is not particularly limited, and methods such as extraction, adsorption, and neutralization can be used as in the case of the metal (b) ions. In the separation liquid, since the metal (b) ions have already been separated, various separation methods can be used, but typically, the metal (a) ions are extracted from the separation liquid by the same manner as described above. It may be separated.

  The extraction method of the ions of the metal (a) can be selected according to the type of the ions of the metal (a), and the extraction agent capable of extracting (or adsorbing) the ions of the metal (a) in the same manner as the metal (b). (It may be called extractant A) may be used. Since the metal (b) ions are already separated in the separation liquid, the extraction agent A is an extractant that does not necessarily extract the metal (b) ions as long as the metal (a) ions can be extracted. It is not necessary, and the metal (b) ions may be extractable.

  The principle that such an extractant A (or adsorbent A) separates the metal (a) ions from the separation liquid is the same as that of the extractant B (for example, complex formation). And by using such an extractant A, the metal (a) ions are precipitated together with the extractant A, or the metal (a) ions are different from the layer containing other components in the separation liquid. Can be separated from the separation liquid. For example, when the separation liquid is an aqueous solution, by mixing the extractant A and a non-aqueous solvent (hydrophobic solvent) with the separation liquid, a layer (water layer) containing components other than the ions of the metal (a), It can be separated into a non-aqueous solvent layer containing metal (a) ions and extractant A.

  In the extraction, the separation liquid may be acidic, neutral, or alkaline. If it is necessary to adjust the pH of the separation liquid according to the type of the extractant A, etc., the pH is adjusted by appropriately adding a neutralizing agent, an acid component, an alkali component, etc. to the separation liquid. May be.

  In addition, as extraction agent A in the case of extracting nickel ion etc. on neutral conditions, for example, oxime type extraction agent (for example, “LiX-84I” manufactured by Cognis Japan Co., Ltd.) or phosphorus type extraction agent ( For example, Daihachi Chemical Industry Co., Ltd., "PC-88A" etc.) etc. can be utilized.

  Although the usage-amount of the extractant A is based also on a kind, it is 10-100 weight part with respect to 1 weight part of ions of a metal (a), Preferably it is 20-50 weight part, More preferably, it is 30-40 weight. It may be about a part.

  The ions of metal (a) separated using extractant A may be converted into metal hydroxides as they are, but preferably after separation from extractant A, they may be converted into metal hydroxides. . That is, after extraction, the metal (a) ions are contained in the extractant A, but the metal (a) ions are further separated from the extractant containing such metal (a) ions, and the metal hydroxide is extracted. May be converted to

  The method for separating the metal (a) ions from the extractant A (extractant A containing metal (a) ions) is not particularly limited, but usually, back extraction can be used. The back extraction is not particularly limited as long as the metal (a) ions and the extractant A can be separated, but can be typically performed with an acid component (using an acid component). As the acid component, although depending on the type of the extractant A, a strong acid such as sulfuric acid can be usually used. In many cases, the acid component is usually used in the form of an acidic solvent (for example, an aqueous solution containing the acid component) after being dissolved in an appropriate solvent (for example, water or the like). In such a case, the metal (a) ions are separated from the extractant A in the form of an acidic solvent containing the metal (a) ions. Specifically, the extraction agent A containing ions of the metal (a) and an acidic component (or acidic solvent) are mixed (or brought into contact) so that the ions of the metal (a) are acidic components (or acidic). Solvent)) (or separated in the form of an acidic solvent containing metal (a) ions).

(Method for converting metal (a) ion to metal hydroxide)
In the step (1), in a mixed system containing a plurality of metal ions, a specific metal (a) is separated and converted into a metal hydroxide, which is subjected to a solvothermal reaction. By converting to such a metal hydroxide, a metal recovery process from a mixed system containing a plurality of metal ions can be efficiently performed. For example, in this method, the metal can be efficiently recovered by a simple and low-cost process such as adjusting the pH as necessary.

The conversion method to a metal hydroxide is not particularly limited, and a conventional method can be used. For example, if the metal (a) ion is an ion that precipitates or precipitates due to the formation of a hydroxide, the metal (a) ion (or a separation liquid or an acidic solvent containing the metal (a) ion) and water By contacting an oxide ion source [for example, alkali metal hydroxide (for example, sodium hydroxide, potassium hydroxide, etc.), alkaline earth metal hydroxide (calcium hydroxide, etc.)] A hydroxide can be obtained. In the hydroxide, the metal (a) ions are not usually reduced, and the valence of the hydroxide is the same as the valence of the metal (a) in the mixed solution. For example, when a metal (a) ion is Ni ^2+, it is converted to Ni (OH) ₂ .

  The metal hydroxide thus obtained is subjected to a solvothermal reaction in the presence of a specific organic solvent (C1).

(Organic solvent (C1))
The organic solvent (C1) is not particularly limited as long as it can reduce the metal (a) ion (or metal hydroxide) in the solvothermal reaction. For example, alcohols {for example, alkanol (for example, methanol, C _1-20 alkanols such as ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, decanol, dodecanol, preferably C _1-12 alkanols, more preferably C _1-8 alkanols, especially C _1-4 alkanols) , cycloalkanols (e.g., cyclopentanol, C _5-10 cycloalkanol such as cyclohexanol), glycol monoalkyl ethers [e.g., an alkane diol mono alkyl ethers (e.g., methoxyethanol, ethylene glycol _{C 2-6} alkanediol mono _{C 1-6} alkyl ethers such as monoethyl ether, preferably _{C 2-4} alkane diol mono _{C 1-4} alkyl ether), poly alkanediol monoalkyl ethers (e.g., diethylene glycol monomethyl ether, diethylene glycol Monools such as di to tetra C _2-6 alkanediol mono C _1-6 alkyl ether, preferably diC _2-4 alkanediol mono C _1-4 alkyl ether)] such as monoethyl ether; glycol [eg alkanediols (ethylene glycol, propylene glycol, _{C 2-6} alkane diols such as 1,4-butanediol, preferably _{C 2-4} alkane diol), poly alkanediol (e.g., diethylene glycol, Di- to tetra C _2-6 alkane diols such as propylene glycol, preferably di C _2-4 alkanediol), polyols such as polyols having 3 or more hydroxyl groups (e.g., glycerin, etc.)}, ethers [e.g. , Diethyl ether, anisole, dioxane, tetrahydrofuran, alkanediol dialkyl ether (eg, C _2-6 alkanediol di-C _1-6 alkyl ether such as ethylene glycol dimethyl ether), polyalkanediol dialkyl ether (eg, diethylene glycol dimethyl ether or tetra _{C 2-6} alkanediol _{di-C 1-6} alkyl ether), etc.], ketones (acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (e.g., vinegar Acid esters such as methyl and ethyl acetate), amides (formamide, acetamide, N-methylformamide, N-methylacetamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), nitriles (eg acetonitrile) , Benzonitrile, etc.), carbonates (eg, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, etc.). These organic solvents may be used alone or in combination of two or more.

Among these organic solvents, alcohols [for example, alkanols (for example, C _1-4 alkanols such as methanol and ethanol), glycols and the like] are preferable. Among alcohols, glycols, particularly alkanediol (particularly 1,4-butanediol) is preferable. The organic solvent acts as a reducing agent in the solvothermal reaction, and seems to be involved in the reaction process and the dispersion stability of the particles after the reaction, but has a plurality of hydroxyl groups like 1,4-butanediol. The organic solvent can generate metal nanoparticles efficiently because of such excellent dispersion stabilization effect. Moreover, it is easy to produce | generate a metal single particle.

  The ratio (use ratio) of the organic solvent (C1) is, for example, 1 to 200 parts by weight, preferably 5 to 150 parts by weight, more preferably 1 part by weight of the metal hydroxide (or metal (a)). About 10-100 weight part may be sufficient.

(Surfactant)
The solvothermal reaction may be performed in the presence of a surfactant in addition to the organic solvent (C1). When such a surfactant is used in combination, the dispersion stabilization of the metal particles can be further improved, and the stabilized metal particles can be obtained efficiently.

  The surfactant is not particularly limited, and is an oxygen-containing organic compound, a nitrogen-containing organic compound, a sulfur-containing organic compound [eg, sulfides (eg, dialkyl sulfide such as dibutyl sulfide), sulfoxides (eg, dimethyl sulfoxide, etc.). Dialkyl sulfide), sulfur-containing heterocyclic compounds (such as thiophene)], phosphorus-containing organic compounds (such as phosphate esters), and the like. The surfactants may be used alone or in combination of two or more.

Examples of the oxygen-containing organic compound include carboxylic acid. Carboxylic acids include aliphatic monocarboxylic acids [saturated aliphatic monocarboxylic acids (eg, formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, caproic acid, hexanoic acid, capric acid, lauric acid, behenic acid, myristic acid, etc. C _1-30 aliphatic monocarboxylic acid, preferably C _1-24 aliphatic monocarboxylic acid, etc., unsaturated aliphatic monocarboxylic acid (eg C ₄ such as oleic acid, erucic acid, linoleic acid, abietic acid, etc.) _-34 unsaturated aliphatic carboxylic acids, preferably C _10-30 unsaturated aliphatic carboxylic acids)], monocarboxylic acids such as aromatic monocarboxylic acids (such as benzoic acid); aliphatic polycarboxylic acids [eg, aliphatic saturated polycarboxylic acids (e.g., oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, C _2-1, such as sebacic acid Aliphatic saturated polycarboxylic acids, preferably such as C _2-10 aliphatic saturated polycarboxylic acids), aliphatic unsaturated polycarboxylic acids (e.g., maleic acid, fumaric acid, itaconic acid, C _4-14 fatty sorbic acid, and the like Polyunsaturated polycarboxylic acids, etc.], polycarboxylic acids such as aromatic polycarboxylic acids (eg, phthalic acid, trimellitic acid, etc.); hydroxymonocarboxylic acids [aliphatic hydroxymonocarboxylic acids (eg, glycolic acid, C _2-50 aliphatic hydroxy monocarboxylic acids such as lactic acid, oxybutyric acid, glyceric acid, 6-hydroxyhexanoic acid), aromatic hydroxy monocarboxylic acids (such as salicylic acid, oxybenzoic acid, etc.)], hydroxypolycarboxylic acids [ Aliphatic hydroxypolycarboxylic acids (eg, tartronic acid, tartaric acid, citric acid, malic acid And the like, such as _C2-10 aliphatic hydroxypolycarboxylic acid and the like].

Examples of nitrogen-containing organic compounds include amines and amides. The amines may be any of primary amines, secondary amines, and tertiary amines, and in particular primary or secondary amines. Specific amines include, for example, aliphatic amines [eg, propylamine, butylamine, hexylamine, octylamine, decylamine, dodecylamine, laurylamine, tetradecylamine, hexadecylamine, octadecylamine, myristylamine, C _{1-30 alkaneamines} such as dipropylamine, dibutylamine, dioctylamine (preferably _{C4-28 alkaneamines} , more preferably _{C6-24 alkaneamines} , especially _C8-20 alkaneamines); C such as oleylamine _2-30 alkenyl amines (preferably _{C 4-28} alkenyl amines, more preferably _{C 6-24} alkenyl amines, especially _{C 8-20} alkenyl amines); triethylenetetramine, Polya such tetraethylenepentamine Like sharp emission polyamines; and C _5-10 cycloalkyl amines, such as cyclohexylamine, aromatic amines (e.g., aniline, toluidine, anisidine, etc. phenetidine), araliphatic amines (e.g., benzylamine, N- methylbenzylamine Aralkylamines such as amine, phenethylamine and xylylenediamine), heterocyclic amines (eg piperidine, piperazine, pyrrolidine, morpholine, etc.), hydroxyl group-containing amines [eg alkanolamines (eg methylaminoethanol, ethanolamine, And C _2-10 alkanolamines such as diethanolamine, propanolamine, butanolamine, hexanolamine) and the like.

  Of these surfactants, amines are preferred. Among amines, aliphatic amines (for example, saturated or unsaturated aliphatic amines having 6 or more carbon atoms such as oleylamine) are particularly preferable. In particular, when such amines are combined with a multidentate organic solvent (C1) (for example, 1,4-butanediol), the particles can be efficiently dispersed and stabilized.

  The ratio of the surfactant may be, for example, 1 to 200 parts by weight, preferably 5 to 150 parts by weight, and more preferably about 10 to 100 parts by weight with respect to 1 part by weight of the metal hydroxide.

  The ratio (use ratio) between the organic solvent (C1) and the surfactant is the former / the latter (weight ratio) = 95/5 to 5/95 (for example, 90/10 to 10/90), preferably 85. / 15 to 15/85 (for example, 80/20 to 20/80), more preferably about 75/25 to 25/75 (for example, 70/30 to 30/70).

  In addition, you may perform a solvothermal reaction in presence of solvent components other than an organic solvent (C1) and surfactant as needed.

  The solvothermal reaction is usually performed in a non-acidic (that is, neutral or alkaline) mixed solution (reaction mixed solution) from the viewpoint of corrosion of the container. That is, the liquid mixture used for the solvothermal reaction is often neutral or alkaline. In step (1), metal hydroxides (and basic surfactants such as amines) are used, so a non-acidic mixture can be efficiently subjected to a solvothermal reaction. Depending on, the pH of the mixed solution may be adjusted by adding an alkali component or the like.

  The solvothermal reaction is performed under high temperature and high pressure (pressurization). The reaction temperature may be, for example, about 130 to 500 ° C, preferably 150 to 450 ° C, more preferably about 200 to 400 ° C (eg, 250 to 350 ° C). The heat source for the solvothermal reaction is not particularly limited, but the efficiency of recycling can be further enhanced by using waste heat (for example, waste heat in plating).

  The reaction pressure is, for example, 0.5 MPa or more (for example, 0.5 to 30 MPa), preferably 1.0 MPa or more (for example, 1.0 to 25 MPa), more preferably 2 MPa or more (for example, 2.0 to 20 MPa), particularly about 2.5 MPa or more (for example, 2.5 to 15 MPa).

  The reaction time is, for example, 10 minutes or more (for example, 15 minutes to 24 hours), 20 minutes or more (for example, 30 minutes to 24 hours), preferably 40 minutes or more (for example, 50 minutes to 12 hours), more preferably It may be 1 hour or longer (for example, 1.5 to 6 hours).

  The solvothermal reaction may be performed in a critical state (supercritical state or subcritical state).

  In addition, you may perform solvothermal reaction under inert atmosphere normally. Further, the solvothermal reaction may be performed by either a batch method or a flow method.

[Step (2)]
In the step (2), the mixed solution is subjected to a solvothermal reaction in the presence of an organic solvent (C2) capable of reducing the ions of the metal (a) and not reducing the ions of the metal (b). (A) is generated. That is, in the step (2), in the system in which the ions of the metal (a) and the ions of the metal (b) coexist, the metal particles (A) are directly separated without separating the ions of the metal (a). Generate. In the step (2), at least the metal particles (A) (metal (a) particles) may be generated. As described later, in the present invention, the metal particles (A) and the metal particles (A) are formed by a solvothermal reaction. The particles of metal (b) can also be produced as different particles.

  The organic solvent (C2) is the same as the organic solvent (C1) in that the ions of the metal (a) can be reduced, but does not reduce the ions of the metal (b) (reduction ability for the ions of the metal (b). Do not have). Therefore, the organic solvent (C2) can be selected by a combination of metal (a) ions and metal (b) ions. The method for selecting such an organic solvent (C2) is not particularly limited, but may be selected using the oxidation-reduction potential of the metal (a) ion and the oxidation-reduction potential of the metal (b) ion as indicators. That is, when the redox potential of the organic solvent (C2) is Ec, the redox potential of the metal (a) ions is Ea, and the redox potential of the metal (b) ions is Eb, Eb <Ec <Ea The solvent (C2) may be selected so that

  The oxidation-reduction potential is preferably set by the reaction temperature and reaction pressure in the solvothermal reaction, but if the standard oxidation-reduction potential (25 ° C.) is used, the solvent (C2) can be easily selected, Even when the standard oxidation-reduction potential is used, the same result as that in the reaction temperature or reaction pressure in the solvothermal reaction is often obtained (there is a correlation).

For example, when the metal (a) ion is Ni ²⁺ and the metal (b) ion is Zn ²⁺ , these standard redox potentials (25 ° C.) are −0.26 V and −0.76 V, respectively. Therefore, a solvent having a standard oxidation-reduction potential (25 ° C.) exceeding −0.26 V and less than −0.76 V may be used as the solvent (C2). When a part of the standard redox potential of the solvent or metal ion is not known, the standard redox potential may be measured by a conventional method. Even in such a case, the solvent (C2) can be selected only by measuring a part of the standard redox potential.

As the organic solvent (C2), a solvent similar to the organic solvent (C1) can be used on the premise of the above viewpoint. The preferred solvent (C2) is also the same as the solvent (C1), and alcohols [eg, alkanols (eg, C _1-4 alkanols such as methanol, ethanol, etc.), glycols, etc.] are preferred. Among alcohols, glycols, particularly alkanediol (particularly 1,4-butanediol) is preferable. Such a solvent can easily generate the metal (b) as a metal oxide or the like, and can efficiently separate from the metal (a).

  In addition to the above reasons, alcohols are often located between the redox potential of the metal (a) ion and the redox potential of the metal (b) ion at the redox potential, and can be suitably used. For example, the standard redox potential of methanol (25 ° C) is 0.588V, the standard redox potential of ethanol (25 ° C) is -0.5V, and the standard redox potential of 1,4-butanediol (25 ° C) is- 0.75V.

  The ratio (use ratio) of the organic solvent (C2) is, for example, 1 to 200 parts by weight, preferably 5 to 150 parts by weight, and more preferably about 10 to 100 parts by weight with respect to 1 part by weight of the metal (a). There may be.

  The proportion of the organic solvent (C2) is, for example, 0.5 to 200 parts by weight, preferably 3 to 150 parts by weight, more preferably 1 part by weight of the total amount of the metal (a) and the metal (b). About 5 to 100 parts by weight may be used.

  The solvothermal reaction may be performed in the presence of a surfactant as in the step (1). As the surfactant, the same surfactants as described above can be used, and preferable surfactants are also the same as described above.

  The ratio of the surfactant may be, for example, 1 to 200 parts by weight, preferably 5 to 150 parts by weight, and more preferably about 10 to 100 parts by weight with respect to 1 part by weight of the metal (a).

  Moreover, the ratio of surfactant is 0.5-200 weight part with respect to 1 weight part of total amounts of a metal (a) and a metal (b), Preferably it is 3-150 weight part, More preferably, it is 5- It may be about 100 parts by weight.

  The ratio (use ratio) of the organic solvent (C2) to the surfactant is the former / the latter (weight ratio) = 95/5 to 5/95 (for example, 90/10 to 10/90), preferably 85/15. It may be about 15/85 (for example, 80/20 to 20/80), more preferably about 75/25 to 25/75 (for example, 70/30 to 30/70).

  In addition, you may perform solvothermal reaction in presence of solvent components other than an organic solvent (C2) and surfactant as needed.

  In the solvothermal reaction, the reaction temperature, reaction pressure, and reaction time can be selected from the same ranges as in step (1).

  The solvothermal reaction may be performed in a critical state (supercritical state or subcritical state).

  In addition, the solvothermal reaction is usually performed in a non-acidic (that is, neutral or alkaline) mixed solution (reaction mixed solution) in the same manner as in the step (1).

  In addition, you may perform solvothermal reaction under inert atmosphere normally. Further, the solvothermal reaction may be performed by either a batch method or a flow method.

  Through the step (1) or the step (2), the metal particles (A) are generated. The metal particles (A) are particles obtained by reducing the metal (a) ions. Therefore, the metal particle (A) may be a particle containing a metal (a) having an oxidation number larger than that of the metal (a) ion, and is usually a single metal particle (a metal (a) particle having an oxidation number of 0). It may be. In addition, when the ions of the metal (a) are composed of a plurality of ions, these metals (a) are obtained as separate particles or alloy particles (or composite metal particles), respectively. All (a) are reduced. In the present invention, even when the metal (a) (or ions thereof) is composed of a plurality of metals (or ions thereof), alloy particles containing a plurality of metals (for example, nickel-cobalt) as the metal particles (A). Alloy particles, alloy particles composed of a plurality of noble metals, etc.) can be obtained.

  Since the metal particles (A) are obtained by the solvothermal reaction as described above, the surface of the organic particles is formed with components derived from the organic solvent (C1) or (C2) (and components derived from the surfactant). It is often covered with. That is, the metal particles (A) are usually composed of core particles (metal core particles) composed of the metal (a) and components (and surface activity) derived from the organic solvent (C1) or (C2) on the surface of the core particles. In many cases, it contains an organic layer formed of a component derived from the agent. The metal particles (A) (metal core particles) are present as stabilized particles without being agglomerated (or suppressed agglomeration) even though they are nanoparticles due to such an organic layer. The component derived from the organic solvent (C1) or (C2) constituting the organic layer (and the component derived from the surfactant) is bonded (covalent bond, ionic bond, coordinate bond, etc.), electrostatic force (electrostatic It seems to exist on the surface of the core particle by binding or adsorbing to the surface of the core particle by interaction) or the like.

  The ratio of such an organic layer may be, for example, about 1 to 30% by weight, preferably about 3 to 20% by weight, and more preferably about 5 to 15% by weight with respect to the entire metal particles (A).

  The metal particles (A) are usually obtained as nanoparticles (metal (a) nanoparticles). The average particle diameter of such metal particles (A) may be, for example, about 1 to 800 nm, preferably 5 to 700 nm, more preferably 10 to 500 nm, particularly 20 to 400 nm (for example, 30 to 350 nm). .

  In the step (2), in addition to the metal particles (A) (separately from the metal particles (A)), usually metal (b) particles (metal particles (B)) can also be obtained. That is, in the step (2), the metal (b) particles (B) can be generated together with the metal particles (A) by a solvothermal reaction. In the step (2) of the present invention, since the metal (b) is also made into particles as described above, not only the separation and recovery of the metal (a) but also the separation and recovery of the metal (b) can be performed efficiently. .

  The ions of the metal (b) are generated as particles of the metal compound without being reduced (or while maintaining the oxidation number or valence of the ions of the metal (b)). The metal compound can be selected depending on the composition of the mixed solution and may be a metal sulfide, a metal halide, a metal carbonate or the like, but is usually a metal oxide in many cases. When the metal (b) ions are composed of a plurality of ions, these metals (b) are obtained as separate particles (for example, metal oxide) or composite metal particles (for example, complex oxide). It is done.

  In addition, since the metal particles (B) are also obtained by the solvothermal reaction as described above, the surfaces of the metal particles (B) are components derived from the organic solvent (C1) or (C2) (and the interface). In many cases, it contains a component derived from an activator, for example, an organic solvent (C1) or (C2) or a residue thereof, a surfactant or a residue thereof. That is, the metal particles (B) are usually composed of core particles (metal core particles) composed of the metal (b), and components (and surface activity) derived from the organic solvent (C1) or (C2) on the surface of the core particles. In many cases, it contains an organic layer formed of a component derived from the agent.

  The metal particles (B) are also usually nanoparticles, and the average particle size of the metal particles (B) is, for example, 1 to 800 nm, preferably 5 to 700 nm, more preferably 10 to 500 nm, particularly It may be about 20 to 400 nm (for example, 30 to 350 nm).

In addition, after the solvothermal reaction, the generated metal particles (A) and metal particles (B) can be separated and collected from the reaction solution by a conventional method (for example, filtration, centrifugation, etc.).
Moreover, when producing | generating a metal particle (A) and a metal particle (B) in a process (2), these isolation | separation can be easily isolate | separated using the attribute of a metal particle, etc. For example, since the metal particles (A) are single metal particles, they often exhibit magnetism (particularly ferromagnetic), whereas the metal particles (B) such as metal oxides are weaker than the single metal particles. It is magnetic. In such a case, a particle mixture containing the metal particles (A) and the metal particles (B) recovered by filtration and extraction using the difference in magnetic strength (for example, by applying a magnetism or a magnetic field). These can be separated from

  In the present invention, ions of metal (a) (and metal (b)) can be efficiently recovered. For example, the recovery rate of ions of metal (a) (or metal (b)) separated from the mixed solution is For example, it is 40% by weight or more (for example, 45 to 100% by weight), preferably 50% by weight or more (for example, 55 to 99% by weight), and more preferably 60% by weight or more (for example, 60 to 98% by weight). May be.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  In the examples, the particle size of the particles was measured as follows.

(Particle size measurement method)
It was measured with a scale bar in the field of view of the transmission electron microscope. Moreover, the average particle diameter was calculated as an arithmetic average of the particle diameters of these particles by measuring the particle diameter of each particle in the transmission micrograph with a scale bar.

[Example 1]
(Selective separation of nickel ion and zinc ion)
The created nickel plating simulated waste liquid [acid aqueous solution containing Ni ²⁺ at 5800 ppm by weight, Zn ²⁺ at 95 ppm by weight, SO ₄ ²⁻ at 5895 ppm by weight, pH = 4.8] 0.5 L, organic An organic solvent (hydrocarbon-based) containing 10% by volume of a phosphorus-based extractant (C ₈ H ₁₇ P (O) (OC ₈ H ₁₇ ) OH, trade name “PC-88A”, manufactured by Daihachi Chemical Industry Co., Ltd.) Solvent component: ShellSol D70, manufactured by Shell Chemicals) 440 mL was mixed to separate (separate) an aqueous layer containing nickel ions and an organic layer (extractant layer) containing zinc ions.

  And in order to adjust pH of the isolate | separated water layer to 7, 2.7 g of sodium hydrogencarbonate was added. Nickel aqueous solution adjusted to pH 7 and an organic solvent (solvent component: 20% by volume) of an oxime-based extractant (2-hydroxy-5-nonylacetophenone oxime, trade name LiX-84I (manufactured by Cognis Japan Co., Ltd.)) 488 mL of ShellSol D70 (manufactured by Shell Chemicals) was mixed, and the aqueous layer and the organic layer containing nickel ions were separated (separated).

  Furthermore, nickel ions were back-extracted with a 1.2 mol / L sulfuric acid aqueous solution and separated into an organic layer containing nickel ions (D70 layer containing LiX-84I). The nickel ion concentration of the separated sulfuric acid aqueous solution was 3100 mg / L. The obtained aqueous sulfuric acid solution did not contain zinc ions.

  The separated organic layer containing zinc ions (D70 layer containing PC-88A) was back-extracted with 1.2 mol / L sulfuric acid aqueous solution and separated. The zinc ion concentration in the separated aqueous sulfuric acid solution was 110 mg / L. 98% by weight of zinc was recovered in terms of zinc used in the simulated solution. The obtained aqueous sulfuric acid solution did not contain nickel ions.

(Conversion process to hydroxide)
To 200 mL of the aqueous sulfuric acid solution containing nickel ions obtained above, 20.54 g of sodium hydroxide was added to adjust the pH to 9 to 10 to obtain nickel hydroxide. The obtained nickel hydroxide was washed twice with 100 mL of distilled water and then dried by centrifugation from an acetone suspension. The obtained nickel hydroxide was 1.28 g and could be recovered at a rate of 64% by weight in terms of nickel used in the simulated solution.

(Solbothermal reaction of nickel hydroxide)
35 ml of 1,4-butanediol and 35 ml of oleylamine (35 ml) were placed in a 180 ml glass container, and then 1.17 g of the previously obtained nickel hydroxide was added and stirred. The charging ratio of oleylamine and nickel hydroxide was 25: 1 by weight. The obtained solution was set in an autoclave and sealed, and the inside of the system was purged with argon. Then, the temperature was raised to 300 ° C. over 2 hours, and then kept at 300 ° C. for 2 hours and then allowed to cool. At this time, the pressure in the autoclave was 2.9 MPa. When the autoclave was opened, a reaction liquid containing black precipitates was obtained in the glass container. After centrifuging the resulting precipitate, acetone was added to replace the solvent, and the particles obtained by centrifuging were observed with a transmission electron microscope (TEM). As a result, particles having an average particle size of 300 nm were observed. Was generated.

  After the obtained particles were dried and analyzed by X-ray diffraction (XRD), it was found to be metallic nickel (nickel simple substance). Moreover, when the obtained metallic nickel was analyzed by differential thermal and thermogravimetric simultaneous measurement (TG-DTA), 6.1% by weight of organic substances derived from 1,4-butanediol and oleylamine were present on the surface of the metallic nickel. It was.

[Example 2]
In a glass container, nickel plating waste liquid [Ni ²⁺ is 6000 ppm, Zn ²⁺ is 70 ppm, Fe ²⁺ is 3 ppm, Na ⁺ is 24000 ppm, SO ₄ ²⁻ is 7000 ppm, H ₂ PO ₂ ⁻ is 19000 ppm, HPO ₃ ^{2 -} the 17000Ppm, 10 ppm aqueous solution containing 24000ppm maleic acid, pH = 4.8] 1 kg with a mixture 50 mL [weight obtained was concentrated to 2% ^{Ni 2+,} the ^{Zn 2+} 230 ppm, a ^{Fe 2+,} Na ^{+ =} 8%, SO ₄ ^{2− =} 2.3%, H ₂ PO ₂ ⁻⁻ = 6.3%, HPO ₃ ²⁻ = 5.7%, maleic acid = 12%, pH = 4.6] 35 mL of 1,4-butanediol (35 mL (35 g) for 1 g of nickel) and 35 mL of oleylamine (based on 1 g of nickel) 5 mL (25 g)) was added, the obtained alkaline solution was set in an autoclave and sealed, and the inside of the system was purged with argon, then heated to 300 ° C. over 2 hours, and then kept at 300 ° C. for 2 hours. And then allowed to cool.

  At this time, the pressure in the autoclave was 4 MPa. When the autoclave was opened, a black precipitate was generated in the glass container. The precipitate was centrifuged and filtered and washed with acetone and water. After drying the mixture of nickel particles A (nickel nanoparticles) and zinc oxide particles B (zinc oxide nanoparticles) thus obtained, a magnetic field is applied to the mixture to recover only the nickel particles A by magnetism. And separated from the zinc oxide particles B.

  When the recovered particles A were analyzed (TEM observation), nickel nanoparticles having an average particle diameter of 50 to 500 nm (average particle diameter of 300 nm) were generated. Further, it was confirmed that the particles A did not contain zinc by a scanning electron microscope / energy dispersive X-ray analyzer (SEM-EDS) and inductively coupled plasma emission analysis (ICP emission analysis).

  Further, when the particles A were analyzed by TG-DTA, 6.1% by weight of organic substances derived from 1,4-butanediol and oleylamine were present on the surface of the metallic nickel. The recovery rate of nickel from the waste liquid calculated from this value was 81% by weight.

  On the other hand, when the recovered particles B were analyzed (TEM observation), 10 to 300 nm zinc oxide particles (average particle size 50 nm) were generated. Further, it was confirmed by SEM-EDS and ICP emission analysis that the particles B contain only zinc oxide and no nickel.

  Furthermore, when the particle B was analyzed by TG-DTA, the organic substance derived from 1,4-butanediol and oleylamine was present at 12.3% by weight on the surface of zinc oxide. The recovery ratio of zinc from the waste liquid calculated from this value was 90% by weight.

[Example 3]
In a glass container, a simulated waste liquid containing cobalt [Co ²⁺ is 5000 ppm, Mn ²⁺ is 70 ppm, Fe ²⁺ is 3 ppm, Na ⁺ is 24000 ppm, SO ₄ ²⁻ is 7000 ppm, and H ₂ PO ₂ ⁻ is 19000 ppm on a weight basis. 50 mL of an aqueous solution obtained by concentrating 1 kg of an aqueous solution containing 17000 ppm of HPO ₃ ^2- and 24000 ppm of acetic acid, pH = 4.6] [Co ²⁺ is 2%, Mn ²⁺ is 230 ppm, Fe ²⁺ is 10 ppm, Na ⁺ 8%, SO ₄ ²⁻ 2.3%, H ₂ PO ₂ ⁻ 6.3%, HPO ₃ ²⁻ 5.7%, acetic acid 12% aqueous solution, pH = 4. 4], 35 mL of 1,4-butanediol (35 mL (35 g) for 1 g of cobalt) and 35 mL of oleylamine (based on 1 g of cobalt) 5 mL (25 g)) was added, and the resulting solution was set in an autoclave and sealed. After the system was purged with argon, the temperature was raised to 300 ° C. over 2 hours, and then maintained at 300 ° C. for 2 hours. , Allowed to cool.

  At this time, the pressure in the autoclave was 5.34 MPa. When the autoclave was opened, a black precipitate was generated in the glass container. The precipitate was centrifuged and filtered and washed with acetone and water. After drying the mixture of cobalt particles A (cobalt nanoparticles) and manganese oxide particles B (manganese oxide nanoparticles) thus obtained, only the cobalt particles A are recovered magnetically by applying a magnetic field to the mixture. And separated from the manganese oxide particles B.

  When the recovered particles A were analyzed (TEM observation), cobalt nanoparticles having a particle size of 100 to 600 nm (unshaped particles having an average particle size of 350 nm) were generated. Further, it was confirmed by a scanning electron microscope / energy dispersive X-ray analyzer (SEM-EDS) and inductively coupled plasma emission analysis (ICP emission analysis) that the particles A did not contain manganese.

  Further, when the obtained particle A was analyzed by X-ray diffraction (XRD), it was found to be hexagonal metallic cobalt (cobalt simple substance). Furthermore, when the obtained metallic cobalt was analyzed by differential thermal and thermogravimetric simultaneous measurement (TG-DTA), there was 0.23% by weight of an organic substance (adsorption layer) derived from 1,4-butanediol on the surface of the metallic cobalt. Was. And the collection | recovery ratio of the cobalt from the waste liquid computed from this value was 89 weight%.

  On the other hand, when the recovered particles B were analyzed (TEM observation), manganese oxide particles (average particle diameter of 80 nm) were generated. In addition, it was confirmed by SEM-EDS and ICP emission analysis that the particles B contain only manganese oxide and no cobalt.

  Further, when the particle B was analyzed by TG-DTA, 9.8% by weight of organic substances derived from 1,4-butanediol and oleylamine were present on the surface of the manganese oxide. And the collection | recovery ratio of manganese from the waste liquid computed from this value was 85 weight%.

[Example 4]
In a glass container, the prepared simulated waste liquid containing cobalt and nickel [by weight, Co ²⁺ is 3000 ppm, Ni ²⁺ is 3000 ppm, Mn ²⁺ is 70 ppm, Fe ²⁺ is 3 ppm, Na ⁺ is 24000 ppm, SO ₄ ²⁻ is 70000 ppm, 50 mL of an aqueous solution obtained by concentrating 1 kg of H ₂ PO ₂ ⁻ , 17000 ppm of HPO ₃ ²⁻ , 17000 ppm of HPO ₃ ²⁻ , 24,000 ppm of acetic acid, pH = 4.8, 1% of Co ²⁺ , Ni ²⁺ is 1%, Mn ²⁺ is 230 ppm, Fe ²⁺ is 10 ppm, Na ⁺ is 8%, SO ₄ ²⁻ is 2.3%, H ₂ PO ₂ ⁻ is 6.3%, and HPO ₃ ²⁻ is 5.7. %, An aqueous solution containing 12% acetic acid, pH = 4.4] and 35 mL of 1,4-butanediol (17. mL (17.5 g), 17.5 mL (17.5 g) for 1 g of nickel), 35 mL of oleylamine (17.5 mL (12.5 g) for 1 g of cobalt, 17.5 mL (12 g) for 1 g of nickel 0.5 g)), and the resulting solution was set in an autoclave and sealed, and the inside of the system was purged with argon. Then, the temperature was raised to 300 ° C. over 2 hours, and then kept at 300 ° C. for 2 hours. Allowed to cool.

  At this time, the pressure in the autoclave was 3.70 MPa. When the autoclave was opened, a black precipitate was generated in the glass container. The precipitate was centrifuged and filtered and washed with acetone and water. After drying the mixture of particles A (nickel-cobalt alloy nanoparticles) and manganese oxide particles B (manganese oxide nanoparticles) thus obtained, a magnetic field is applied to the mixture to recover only particles A magnetically. Then, it was separated from the manganese oxide particles B.

  When the recovered particles A were analyzed (TEM observation), rod-shaped particles having a length of 500 nm and a diameter of 30 nm were generated. Further, it was confirmed by a scanning electron microscope / energy dispersive X-ray analyzer (SEM-EDS) and inductively coupled plasma emission analysis (ICP emission analysis) that the particles A did not contain manganese.

  Further, when the obtained particle A was analyzed by X-ray diffraction (XRD), it was a cubic nickel-cobalt alloy (nickel / cobalt (molar ratio) = 6/4) (in the case of nickel alone, cubic crystal). From the fact that cobalt alone is hexagonal, it was found that the crystal system was changed by solid solution).

  Furthermore, when the obtained nickel-cobalt alloy was analyzed by differential thermal and thermogravimetric simultaneous measurement (TG-DTA), the organic matter (adsorption layer) derived from 1,4-butanediol was 0. 0 on the surface of the nickel-cobalt alloy. 3% by weight, 0.07% by weight of organic matter (adsorbed layer) derived from oleylamine was present. And the recovery rate of nickel and cobalt from the waste liquid computed from this value was 93 weight%.

  On the other hand, when the recovered particles B were analyzed (TEM observation), manganese oxide particles (average particle diameter of 100 nm) were generated. Further, it was confirmed by SEM-EDS and ICP emission analysis that the particle B contains only manganese oxide and does not contain cobalt and nickel.

  Further, when the particles B were analyzed by TG-DTA, 8.9% by weight of organic substances derived from 1,4-butanediol and oleylamine were present on the surface of the manganese oxide. And the collection | recovery ratio of manganese from the waste liquid computed from this value was 84 weight%.

  The method of the present invention is useful in various applications as a metal separation method from a mixed solution containing a plurality of metal ions. For example, in the method of the present invention, crystallization can be promoted from waste liquid (such as plating waste liquid) containing valuable metals by solvothermal reaction, and valuable metals can be recycled as particles, and valuable metals can be efficiently recovered. Furthermore, valuable metals can be separated and recovered while adding the function as nanoparticles. In this way, resource saving and reuse of valuable resources can be achieved by recycling, and particles having industrial utility value can be produced.

  In particular, metal nanoparticles have shown great electronic, electrical, optical, magnetic, chemical and mechanical properties that are different from solid materials in the bulk state. This contributes to high functionality, miniaturization, and thinning of products, and can be applied to various applications. For example, metallic nickel can be used as an internal electrode of a multilayer ceramic capacitor, and since it is a nanoparticle, it leads to an increase in the number of laminated layers and an improvement in performance.

Claims (19)

Using a mixed solution containing ions of the metal (a) and ions of the metal (a) and the metal (b) having a different metal type, the following steps (1) or (2) are used to obtain the metal (a). A method for producing metal particles (A) of metal (a) by reducing ions.
(1) After separating ions of metal (a) from the mixed liquid and converting them into metal hydroxides of metal (a), in the presence of an organic solvent (C1) capable of reducing the ions of metal (a), Step (2) in which the metal hydroxide is subjected to a solvothermal reaction to produce metal particles (A), the mixture can reduce the ions of the metal (a) and does not reduce the ions of the metal (b) Step of generating metal particles (A) by subjecting to a solvothermal reaction in the presence of an organic solvent (C2)   The production method according to claim 1, wherein the ionization tendency of the metal (b) is larger than the ionization tendency of the metal (a).   The method according to claim 1 or 2, wherein the difference between the standard oxidation-reduction potential (25 ° C) of the metal (a) and the standard oxidation-reduction potential (25 ° C) of the metal (b) is 0.2 V or more.   The metal (a) is at least one selected from Group 8 metal of the periodic table, Group 9 metal of the periodic table, Group 10 metal of the periodic table, Group 11 metal of the periodic table, and the metal (b) Selected from Table Group 4 metal, Periodic Table Group 5 metal, Periodic Table Group 6 metal, Periodic Table Group 7 metal, Periodic Table Group 8 metal, Periodic Table Group 12 metal and Periodic Table Group 13 metal The production method according to claim 1, wherein the production method is at least one kind.   The metal (a) is at least one selected from cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, and gold, and the metal (b) is titanium, zirconium, manganese, zinc, gallium. The manufacturing method in any one of Claims 1-4 containing at least 1 sort (s) selected from indium.   The manufacturing method according to claim 1, wherein the metal (a) includes a plurality of metals, and alloy particles including the plurality of metals are generated as the metal particles (A).   The manufacturing method according to claim 1, wherein the mixed solution is a plating waste solution.   The manufacturing method according to any one of claims 1 to 7, wherein in the step (1), ions of the metal (a) are separated by extracting and separating the ions of the metal (b) from the mixed solution.   9. In the step (1), the metal (b) ions are separated from the mixed solution by using an extractant that does not extract the metal (a) ions and can extract the metal (b) ions. The manufacturing method as described.   In the step (1), the metal (b) ions are separated, and the metal (a) ions are further separated from the separation liquid containing the metal (a) ions by extraction and converted into metal hydroxides. Item 10. The manufacturing method according to Item 8 or 9.   In the step (1), ions of the metal (a) are separated using an extractant, and the metal (a) ions are extracted from the extractant containing the ions of the metal (a) by back extraction with an acid component. The manufacturing method in any one of Claims 8-10 which isolate | separates with the form of the acidic solvent containing the ion of a), and converts into a metal hydroxide.   The production method according to claim 1, wherein the organic solvent (C1) or (C2) is an alcohol.   The production method according to any one of claims 1 to 12, wherein the organic solvent (C1) or (C2) is a glycol.   The manufacturing method according to any one of claims 1 to 13, wherein the organic solvent (C1) or (C2) is 1,4-butanediol.   Furthermore, the manufacturing method in any one of Claims 1-14 which perform solvothermal reaction in presence of amines.   The metal particle (A) is a nanoparticle comprising a core particle composed of the metal (a) and an organic layer formed with a component derived from the organic solvent (C1) or (C2) on the surface of the core particle. Item 16. The production method according to any one of Items 1 to 15.   The process according to any one of claims 1 to 16, wherein in step (2), the metal particles (B) of the metal (b) are produced together with the metal particles (A) by a solvothermal reaction.   The method according to claim 17, wherein the metal particles (A) are single metal particles, and the metal particles (B) are metal oxide particles.   The production method according to claim 17, wherein the metal particles (A) are alloy particles and the metal particles (B) are metal oxide particles.