JP2013221182A - Element separation and recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an element separation and recovery method by which selectivity and recovery efficiency of an element such as valuable metal, can be considerably improved, a substance used for recovery of the element can be reused and a chelating agent is not required to be used even when a metal is separated and recovered as the element.SOLUTION: Zonyl (R) FSA and THF are added into a vessel 1 in which solution 2 containing rare-earth metal RE being a target substance is contained. Successively, pH of the solution 2 is set to be about pH 4 of <pH 6.5 with a pH buffer to develop phase separation, and the rare-earth metal RE is extracted in a cohered liquid-phase. Sodium hydroxide aqueous solution is mixed into the cohered liquid phase 10 to raise the pH, and the hydroxide 12 of the rare earth metal RE is extracted. The aqueous solution 11 in which the rare-earth metal RE is extracted, is filtered to recover the hydroxide 12 of the rare-earth metal RE. The remaining Zonyl (R) FSA and THF in the solution, are reused after the pH is adjusted.

Description

  The present invention relates to an element separation and recovery method for recovering elements such as rare earths and valuable metals selectively and efficiently from a solution.

  Currently, rare metals are materials that support advanced technology. Rare metals are used in electronic devices such as mobile phones and personal computers used in normal daily life, or home appliances. These electronic devices and home appliances are often disposed of as industrial waste after use, and are disposed of in the mountains and towns, causing problems.

  These electronic devices and home appliances contain precious metals and rare metals, which are recyclable resources, and are called “urban mines”. Japan is a country that consumes about 10% of the world's mineral resources in a year, but relies on imports for most rare metals. Japan is a country with scarce domestic resources that is almost 100% self-sufficient.

  However, so-called urban mines have higher resource mining rates than underground mines. Thus, an urban mine is a treasure trove of resources, and it is very useful to secure resources by recycling rare metals from the urban mine.

  On the other hand, as a method for separating metals in analytical chemistry, a solvent extraction method using two kinds of solvents that do not mix with each other is mainly used. However, in the solvent extraction method, the extract moves through the interface between the aqueous phase and the organic phase. Therefore, vigorous shaking and time are required to increase the extraction efficiency in the solvent extraction method. In addition, the solvent extraction method has problems such as complicated operation of an apparatus such as a separatory funnel, a large amount of organic solvent is required for extraction of the target substance and cleaning of the apparatus, and a large amount of waste liquid is generated. is there.

  As a new solvent extraction method that can solve these problems, a separation and concentration method using phase separation from a homogeneous solution has been proposed. This separation and concentration method can be separated and concentrated by a quick and simple operation. This separation and concentration method includes a homogeneous liquid-liquid extraction method (Non-Patent Document 1), a homogeneous solid-phase extraction method (Non-Patent Document 2), and an aqueous two-phase extraction method depending on the difference in the form of precipitation after phase separation from a homogeneous solution. (Non-patent document 3). Among these extraction methods, the homogeneous liquid-liquid extraction method has the advantage that since there is no interface between the aqueous phase and the organic phase, the interface at the molecular level is infinite and simple without mechanical shaking operation ( Non-patent document 4).

Igarashi Goro, Oshite Shigekatsu, “Bunseki” 9, p702-709 (1997). Toru Saito, Chiyo Matsubara, Masataka Hiraide, “Analytical Chemistry”, Vol. 52, No. 4, p221-229 (2003). Yanji Anzai, Yoshifumi Akama, “Analytical Chemistry”, Vol. 52, No. 5, p337-340 (2003). Hitoshi Yamaguchi, Shinji Ito, Goro Igarashi, Go Kobayashi, “Analytical Chemistry”, Vol. 54, No. 3, p 227-230 (2005).

  However, these methods have problems in that the selectivity and recovery efficiency of valuable metals including rare metals and rare earths are low, and the substances used for recovery of valuable metals cannot often be reused. In addition, even when the selectivity and recovery efficiency of valuable metals are high, it is necessary to use a chelating reagent in the separation and recovery of valuable metals, so many chemicals are required when separating and recovering elements such as metals. (Non-patent document 4).

  The present invention has been made in view of the above, and its purpose is to greatly improve the selectivity and recovery efficiency of elements such as valuable metals and to reuse the materials used for the recovery of elements. It is another object of the present invention to provide an element separation and recovery method that does not require the use of a chelating reagent even when metals are separated and recovered as elements.

  In order to solve the above-described problems and achieve the above object, an element separation and recovery method according to the present invention includes tetrahydrofuran and lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) in a solution containing the element. Thio] propionate, alkyl: a surfactant addition step for adding hexyl to decanyl, a pH adjustment step for adjusting the pH of the solution to less than 6.5, and a liquid phase recovery step for recovering the aggregated liquid phase from the solution The pH of the agglomerated liquid phase is raised using an alkaline solution to separate the elements from tetrahydrofuran and lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) thio] propionate, alkyl: hexyl-decanyl. And a separating step.

  The element separation and recovery method according to the present invention is characterized in that, in the above invention, the pH of the solution is adjusted to 3.5 or more and 5.0 or less in the pH adjustment step.

  The element separation and recovery method according to the present invention is characterized in that, in the above-mentioned invention, the element hydroxide is precipitated by an alkaline solution in the separation step.

  In the element separation and recovery method according to the present invention, in the above invention, the elements are Sc, Cr, Fe, Ga, Y, Zr, Pd, Ag, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb. , Dy, Ho, Er, Tm, Tb, and Lu, at least one selected from the group.

  According to the element separation and recovery method of the present invention, it is possible to greatly improve the selectivity and recovery efficiency of the element to be separated and recovered, and it is possible to reuse the material used for element recovery, Even when the element to be separated and recovered is a metal, the element can be selectively separated and recovered without using a chelating reagent.

FIG. 1 is a schematic diagram showing an element separation and recovery method according to an embodiment of the present invention. FIG. 2 is a flowchart showing an element separation and recovery method according to an embodiment of the present invention. FIG. 3 is a chart showing an example of a recovery rate when an element is recovered by an element separation and recovery method according to an example based on one embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals. Further, the present invention is not limited to the embodiments described below.

  First, an element separation and recovery method according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram for explaining an element separation and recovery method according to this embodiment. FIG. 2 is a flowchart showing an element separation and recovery method according to this embodiment.

In the element separation and recovery method according to one embodiment of the present invention, a uniform liquid-liquid extraction method is employed. First, as shown in FIG. 1A, a solution 2 containing a rare earth element (rare earth) RE, which is an example of an extraction substance (target substance) as an element, is prepared in a container 1. The solution 2 may contain an alkali metal (alkali metal ion), a metal element (metal ion), or a non-metal element known not to be recovered by the separation and recovery method according to the embodiment, Here, it is assumed that various elements M ₁ , M ₂ , and M ₃ are included in addition to the rare earth RE as the target material.

  The rare earth RE is an element name (element symbol: atomic number) as scandium (Sc: 21), yttrium (Y: 39), lanthanum (La: 57), cerium (Ce: 58), praseodymium (Pr: 59), neodymium (Nd: 60), promethium (Pm: 61), samarium (Sm: 62), europium (Eu: 63), gadolinium (Gd: 64), terbium (Tb: 65), dysprosium (Dy: 66) ), Holmium (Ho: 67), erbium (Er: 68), thulium (Tm: 69), ytterbium (Yb: 70), and lutetium (Lu: 71).

  Valuable metal ions are ions of metals selected from heavy metals and light metals. Here, heavy metals are titanium (Ti: 22), iron (Fe: 26), cobalt (Co: 27), nickel (Ni: 28), copper (Cu: 29), zinc (Zn: 30), gallium. (Ga: 31), Y, zirconium (Zr: 40), niobium (Nb: 41), ruthenium (Ru: 44), palladium (Pd: 46), cadmium (Cd: 48), indium (In: 49), Tantalum (Ta: 73), gold (Au: 79), mercury (Hg: 80), lead (Pb: 82), bismuth (Bi: 83), and lanthanoid metals (La, Ce, Pr, Nd) which are rare earth REs , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). Light metals include Sc and aluminum (Al: 13), beryllium (Be: 4), magnesium (Mg: 12), calcium (Ca: 20), strontium (Sr: 38), barium (Ba: 56) And an alkaline earth metal such as radium (Ra: 88).

  Rare earth REs and valuable metal ions are crushed into various samples that are thought to contain these ions, electronic devices such as mobile phones and personal computers, or home appliances, and are used as acids such as aqua regia, sulfuric acid, hydrochloric acid, or nitric acid. It may be prepared from a solution obtained by dissolving in a solution.

  Then, as shown in FIG. 2, water-soluble tetrahydrofuran (THF) represented by the following structural formula (1) is added to the solution 2 (step ST1). In addition, although mentioned later for details, THF used for the uniform liquid-liquid extraction method which is the separation-and-recovery method by this one embodiment is reused for a part or all of this THF.

……（１）

...... (1)

Subsequently, “lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) thio] propionate, alkyl: hexyl to decanyl” represented by the following structural formula (2), which is a fluorine-based surfactant. (Lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) thio] propionate, alkyl: hexyl-decanyl) (Zonyl FSA) is added (step ST2). This fluorosurfactant is represented by the following structural formula (2). The molecular formula (chemical formula) of this fluorosurfactant is represented by CF ₃ (CF ₂ ) _n CH ₂ CH ₂ SCH ₂ CH ₂ CH ₂ COOH (n = 6 to 10), preferably CF _{3 (CF 2) n CH 2 CH} 2 SCH 2 CH 2 CH 2 COOH (n = 6~8, alkyl: hexyl-octyl) those are used. In addition, although mentioned later for details, the fluorine-type surfactant used for the uniform liquid-liquid extraction method which is the separation-and-recovery method by this one embodiment is reused for a part or all of this fluorine-type surfactant. .

……（２）

(2)

Here, examples of the fluorosurfactant include PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). According to the knowledge of the present inventor, these PFOA and PFOS. Presents a strong acid and is designated as a second type monitoring substance, which is not preferable for use. On the other hand, the above-mentioned zonyl FSA has a spacer such as “—CH ₂ CH ₂ SCH ₂ CH ₂ —” in its structure. In addition, this zonyl FSA does not protonate unless it has a very low pH, for example, about pH 1 or less. Therefore, according to the study of the present inventor, it is desirable to employ zonyl FSA as the fluorosurfactant used for element separation and recovery.

  Thus, in steps ST1 and ST2, as shown in FIG. 1B, the fluorosurfactant and THF are added to the solution 2. Note that these steps ST1 and ST2 may be performed simultaneously.

Then, it transfers to step ST3 and performs the stirring process which stirs lightly the solution 2 to which the fluorine-type surfactant was added. Subsequently, the process proceeds to step ST4, and a pH adjusting buffer solution (pH buffer) such as acetic acid (CH ₃ COOH) or sodium acetate (CH ₃ COONa) is added. Thus, the hydrogen ion exponent pH of the metal solution is set to less than pH 6.5 where phase separation may occur, preferably pH 5.0 or less, more preferably about 4.0, where phase separation occurs. The pH value at this time is preferably set to pH = 3.5 or more in consideration of efficient element separation and recovery.

Then, it transfers to step ST5, for example, installs the container 1 in a centrifuge and performs centrifugation. Here, the rotation speed of the centrifuge is, for example, 2500 rpm, and the processing time is, for example, 20 minutes. Thus, as shown in FIG. 1 (c), in the container 1, the solution 2, and a large amount of liquid phase containing the various elements other than THF and analyte M _1, M _2, M _3, rare earth RE, fluorine Separation into two phases with a small amount of liquid phase 10 containing a system surfactant and THF. At this time, most of the rare earth RE contained in the solution 2 is extracted into a small amount of the liquid phase 10.

  Thereafter, the process proceeds to step ST6, and the aggregated liquid phase 10 is separated from the solution 2 as shown in FIG. At the same time, as shown in FIG. 1 (e), the supernatant of the remaining solution 2 from which the rare earth RE has been separated and recovered is recovered. Here, the method for separating the supernatant liquid from the solution 2 and the agglomerated liquid phase is not particularly limited, and a separation method known in the art such as suction of the agglomerated liquid phase or supernatant liquid or a specific gravity using a funnel with a cock. It is possible to employ a method such as separation of an agglomerated liquid phase or a supernatant liquid due to the difference. The conditions for this separation method are not particularly limited, and can be set as appropriate according to the agglomerated liquid phase generated.

  By the above-described steps ST1 to ST6, the target material can be extracted into the liquid phase 10 in which the fluorosurfactant is aggregated. Then, the process proceeds to step ST7, and as shown in FIG. 1 (f), for example, sodium hydroxide (NaOH) having an agglomerated liquid phase 10 and an alkaline aqueous solution higher than pH 7.0, preferably pH 12-13. ) And an aqueous solution. Moreover, in order to replenish the THF consumed up to this stage, a small amount of an aqueous solution of THF is added as necessary. Thereafter, the process proceeds to step ST8.

In step ST8, for example, a rare earth RE hydroxide 12 such as RE (OH) ₃ is deposited as a solid on the fluorosurfactant and the aqueous solution 11 of THF. Then, as shown in FIG. 1 (g), the rare earth RE hydroxide 12 is separated from the solution of the fluorosurfactant and THF by, for example, filtration. Thereby, the hydroxide 12 of the rare earth RE is recovered.

At this time, the aqueous solution 11 after the rare earth RE is recovered contains a fluorosurfactant and THF. Therefore, the process proceeds to step ST9, and the pH of the aqueous solution 11 from which the hydroxide 12 is separated and recovered in step ST8 described above is adjusted for pH adjustment such as acetic acid (CH ₃ COOH) and sodium acetate (CH ₃ COONa). By adding a buffer solution, the pH is adjusted to 6.5 or more, preferably pH 7.0 or more and 8.0 or less, which does not cause phase separation. Thereby, the fluorosurfactant and THF can be recovered in a state of an appropriate pH value. In addition, conventionally well-known method is employable for pH adjustment of this aqueous solution 11. FIG. The thus recovered fluorosurfactant and THF are reused for further separation and recovery according to this embodiment and other applications.

  Next, examples based on the above-described embodiment will be described. In addition, this invention is not limited to this Example. In addition, the following apparatuses are used for the analysis of the characteristic in an Example. Specifically, for the measurement of the metal concentration, an ICP emission spectroscopic analyzer (iCAP6300 type: manufactured by Thermo Fisher) was used. A pH meter (F-51: manufactured by HORIBA) was used for pH measurement.

In Example 1, zonyl FSA is used as the fluorosurfactant based on the separation and recovery method according to the above-described embodiment. And the volume ratio of each substance in the system (ZonylFSA-THF-H ⁺ system) for separating and recovering the target substance is
Solution containing target substance: THF: Zonyl FSA: pH buffer = 5: 6: 5: 4
To be.

  That is, in Example 1, when the solution containing the target substance is 5 ml, for example, 6 ml of THF, 5 ml of zonyl FSA having a concentration of 5% by weight, and 4 ml of pH buffer are used in the separation and recovery process.

  In the system for separating and recovering the target material, the amount of THF can be selected from a range of 10 to 50% with respect to the solution 2 containing the target material. The zonyl FSA having a concentration of 5% by weight can be changed within a range of 1/500 or more and 1 or less with respect to the volume of the metal solution containing the target substance. That is, when the solution containing the target substance is 5 ml, it is possible to appropriately select zonyl FSA from the range of 10 μl or more and 5 ml or less. In this case, the volume of the precipitated phase of the zonyl FSA becomes a value proportional to a linear shape passing through the origin with respect to the amount of the zonyl FSA used.

Then, according to the element separation and recovery method according to the above-described embodiment, an experiment was conducted to separate and recover various target substances in the ZonylFSA-THF-H ⁺ system. As a result, the results shown in FIG. 3 were obtained for each target material. In FIG. 3, the upper part of each column is the element name, the lower part is the recovery rate (%), and the lanthanoid series and actinoid series are shown in separate separate columns.

From FIG. 3, in the separation and recovery method in the ZonylFSA-THF-H ⁺ system according to this example, the lanthanoid metal excluding Sc, Cr, Fe, Ga, Y, Zr, Pd, Ag, and Pt, and Ce and Pm. In (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, Lu), it was confirmed that the recovery rate was 80% or more. Conversely, in silicon (Si), phosphorus (P), Ca, arsenic (As), selenium (Se), rhodium (Rh), indium (In), tin (Sn), antimony (Sb), and Au The recovery rate was 0%, and it was confirmed that the selectivity in the separation and recovery of elements was extremely high.

  According to one embodiment of the present invention described above, the selectivity and recovery efficiency of elements such as valuable metals typified by rare earths can be greatly improved, and the fluorine-based surfactant used for element recovery And THF can be reused for the separation and recovery of the next element. Furthermore, even in the case of separating and recovering metals, it is not necessary to use any chelating reagent that has been necessary in the past, and it is possible to reduce the type and amount of chemicals used. In addition, according to this embodiment, valuable metal, which is a kind of target material, can be recovered with high selectivity from electronic devices such as mobile phones and personal computers, or home appliances. It becomes possible to promote the use greatly.

  Although one embodiment and example of the present invention have been specifically described above, the present invention is not limited to the above-described one embodiment and example, and various modifications based on the technical idea of the present invention. Is possible. For example, the numerical values and elements given in the above-described embodiment and examples are merely examples, and different numerical values and elements may be used as necessary.

  In the above-described embodiment, the case where the rare earth is contained in the solution 2 has been described as an example. However, the element contained in the solution 2 is not necessarily limited to the rare earth. It is possible to use these elements.

  Further, in the above-described embodiment, a sodium hydroxide aqueous solution is used as an aqueous solution to be mixed with the liquid phase 10 after separating the agglomerated liquid phase 10, but the aqueous solution is not necessarily limited to the sodium hydroxide aqueous solution. Instead, various alkaline aqueous solutions such as lithium hydroxide (LiOH) and potassium hydroxide (KOH) can be used.

In the above-described embodiment, acetic acid or sodium acetate is used as the pH buffer. However, the pH buffer is not necessarily limited to acetic acid or sodium acetate, but hydrochloric acid (HCl) or sodium tetraborate (Na ₂ B ₄ O). It is also possible to use other substances such as ₇ ).

1 Container 2 Solution 10 Liquid Phase 11 Aqueous Solution 12 Hydroxide M ₁ , M ₂ , M ₃ Various Elements RE Rare Earth

Claims (4)

A surfactant addition step of adding tetrahydrofuran and lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) thio] propionate, alkyl: hexyl to decanyl to the element-containing solution;
A pH adjusting step for adjusting the pH of the solution to less than 6.5;
A liquid phase recovery step for recovering an aggregated liquid phase from the solution;
The pH of the aggregated liquid phase is increased using an alkaline solution, the tetrahydrofuran and the lithium 3-[(1H, 1H, 2H, 2H-fluoroalkyl) thio] propionate, alkyl: hexyl to decanyl, and the element And a separation step for separating
A method for separating and recovering an element, comprising:   2. The element separation and recovery method according to claim 1, wherein in the pH adjustment step, the pH of the solution is adjusted to 3.5 or more and 5.0 or less.   The element separation / recovery method according to claim 1 or 2, wherein, in the separation step, a hydroxide of the element is precipitated by the alkaline solution.   The element is composed of Sc, Cr, Fe, Ga, Y, Zr, Pd, Ag, Pt, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, and Lu. The element separation / recovery method according to any one of claims 1 to 3, wherein the element is at least one selected from the group.

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