JP2011231366A - Valuable metal recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valuable metal recovery method that has excellent valuable metal selectivity and recovery efficiency, and furthermore is capable of reusing materials that have been used in the recovery of a valuable metal.SOLUTION: The valuable metal recovery method is characterized by including the following steps (a) to (c): (a) a step for preparing an aqueous solution that contains valuable metal ions and a pH-responsive polymer using formula (I) as a constituent unit and that has a pH higher than 6.4; (b) a step for lowering the pH of the aqueous solution below 6.4 and forming an aggregate of the pH-responsive polymer and the valuable metal; and (c) a step for recovering the aggregate from the aqueous solution.

Description

  The present invention relates to a selective and efficient method for recovering valuable metals using a pH-responsive polymer having a specific structure.

  “Rare metal” supports the current advanced technology. Rare metals are also used in electronic devices such as mobile phones and personal computers, which are indispensable for our daily lives, as well as home appliances. These electronic devices and home appliances are often disposed of as industrial waste after use, and in recent years, they have come to be discarded in the mountains and towns.

  These are called "urban mines" because they contain recyclable resources, precious metals and rare metals. Although Japan is a country that uses about 10% of the world's mineral resources in one year, it is a country with scarce domestic resources that it is said that almost all of the rare metals depend on imports, and that almost 100% can be self-sufficient.

  However, in fact, urban mines have higher resource mining rates than underground mines, so urban mines are a treasure trove of resources, and it is very useful to secure resources by recycling rare metals from these urban mines (non- Patent Document 1).

  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 movement of the extract is performed through the interface between the aqueous phase and the organic phase, so that vigorous shaking is required to increase the extraction efficiency, and the operation of equipment such as a separatory funnel is complicated. There are problems such as that 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 produced.

  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. Depending on the precipitation form after phase separation from a homogeneous solution, a uniform liquid-liquid extraction method (Non-patent Document 2), a homogeneous solid-phase extraction method (Non-patent) Document 3) and aqueous two-phase extraction method (Non-patent Document 4). Among these, the homogeneous solid-phase extraction method has an advantage that it is easy to handle after phase separation because the precipitated phase is solid.

  As a collection medium for homogeneous solid-phase extraction, temperature-responsive polymers that have undergone reversible hydrophilic and hydrophobic phase transitions with changes in solution temperature have been used so far. Research applied to the separation and concentration of complexes (Non-Patent Document 5) and hydrophobic organic compounds (Non-Patent Documents 6 and 7) has been reported.

  However, these methods have problems such as poor selectivity and recovery efficiency of valuable metals including rare metals, and often the substances used for recovering valuable metals cannot be reused.

Eiichi Yamaguchi, “Science of Rare Metals”, Nikkan Kogyo Shimbun, (2008). 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). Kazuyo Tachain, Nobuo Uehara, Tokuo Shimizu, “Analytical Chemistry”, Vol. 50, No. 4, p257-262 (2001). Toru Saito, Yuki Yoshida, Chiyo Matsubara, “Analytical Chemistry”, Vol. 51, No. 10, p969-971 (2002). Matsubara Chiyo, Kikuchi Nobuyuki, Takamura Kiyoko, “Analytical Chemistry”, Vol. 44, No. 4, p 311-312 (1995).

  Therefore, an object of the present invention is to provide a method for recovering valuable metals that has good selectivity and recovery efficiency of valuable metals and that can reuse a material used for recovering valuable metals.

  As a result of diligent research to solve the above problems, the present inventors have improved the selectivity and recovery rate of valuable metals among metals by utilizing a pH-responsive polymer having a specific structure for metal recovery. And the present inventors have found that the pH-responsive polymer used for the recovery can be reused.

を構成単位とするｐＨ応答性ポリマーと有価金属イオンを含有し、そのｐＨが６
.４より高い水溶液を調製する工程
（ｂ）前記水溶液のｐＨを６.４より低くし、ｐＨ応答性ポリマーと有価金属の凝集物
を形成させる工程
（ｃ）前記水溶液から凝集物を回収する工程
を含むことを特徴とする有価金属の回収方法である。 That is, the present invention includes the following steps (a) to (c),
(A) The following formula (I)

A pH-responsive polymer having a structural unit and a valuable metal ion, and the pH is 6
A step of preparing an aqueous solution higher than .4 (b) a step of lowering the pH of the aqueous solution below 6.4 to form an aggregate of a pH-responsive polymer and valuable metals (c) a step of recovering the aggregate from the aqueous solution A method for recovering valuable metals.

  The method for recovering valuable metals according to the present invention uses a pH-responsive polymer having a specific structure, enables easy operations such as mixing, pH adjustment, filtration, etc., such as electronic devices such as mobile phones and personal computers, or home appliances. Valuable metals can be recovered with good selectivity. In particular, when recovering ions of In, Au, Ru, Pd, Pb, Hg, Cd, Cu, Al, Fe, and lanthanoid metals by the valuable metal recovery method of the present invention, other metals are contained. Even in this case, it can be selectively and efficiently recovered.

  The valuable metal recovery method of the present invention can also recover and reuse the pH-responsive polymer used for recovering the valuable metal.

^{1 is} a ¹ H-NMR spectrum of Poly (VEBA) s produced in Reference Example 3 (0 to 10 ppm). It is a ¹³ C-NMR spectrum of Poly (VEBA) s produced in Reference Example 3 (0 to 200 ppm). It is a figure which shows the result of the light absorbency measurement in Example 5 (In the figure, A is the spectrum of the filtrate before collection | recovery of Poly (VEBA) s, B is the spectrum of the filtrate after collection | recovery of Poly (VEBA) s).

In the step (a) of the valuable metal recovery method of the present invention (hereinafter referred to as “the present invention recovery method”), a pH-responsive polymer having the following formula (I) as a structural unit and valuable metal ions are contained, and the pH An aqueous solution is prepared with a pH greater than 6.4.

  A pH-responsive polymer (hereinafter, simply referred to as “pH-responsive polymer”) having the above formula (I) as a structural unit causes a reversible hydrophilic and hydrophobic phase transition around pH 6.4. Therefore, the pH-responsive polymer is uniformly dissolved in water in the pH range higher than pH 6.4, but in the pH range lower than pH 6.4, the phase due to the rapid dehydration of the polymer near pH 6.4 and the accompanying hydrophobic interaction. It has the characteristic that a transition takes place, resulting in insolubility in water.

  The pH-responsive polymer has a molecular weight of 5,000 to 100,000, preferably 15,000 to 40,000, and a molecular weight distribution (Mw / Mn) of 1.0 to 10,000. Examples thereof include 2.0, preferably 1.4 to 1.6. The closer the molecular weight distribution is to 1, the sharper the phase transition behavior is.

  Since the pH-responsive polymer used in the present invention is insoluble in ordinary organic solvents, the above-mentioned weight average molecular weight, number average molecular weight and molecular weight distribution are poly (4- [2- (vinyloxy)) which is a precursor. -Ethoxy] -ethyl benzoate) is estimated from the weight average molecular weight, number average molecular weight and molecular weight distribution. Specifically, the weight average molecular weight, number average molecular weight and molecular weight distribution of poly (4- [2- (vinyloxy) -ethoxy] -ethyl benzoate) are determined from a standard polystyrene calibration curve by gel permeation chromatography (GPC). It was.

  The method for preparing the pH-responsive polymer is not particularly limited as long as the precursor and the polymerization conditions are appropriately selected so that the compound of formula (I) can be prepared. For example, the pH-responsive polymer is obtained by reacting ethyl 4-hydroxybenzoate with ethyl chloroethyl vinyl ether (ethyl 4- (vinyloxyethoxy) benzoate (VEBAE) under an inert gas such as argon and under ice temperature. Thus, 1-butoxyethyl acetate (IBEA) obtained by reacting isobutyl vinyl ether and acetic acid as a starting species can be prepared by living cationic polymerization with an activator such as tin chloride for about 1 hour.

  On the other hand, the valuable metal ion is a metal ion selected from heavy metals and light metals. Here, the heavy metal is a metal selected from Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Ru, Pd, Cd, In, Ta, Au, Hg, Pb, Bi, and a lanthanoid metal. It is. The light metal is a metal selected from the group consisting of Sc, Al and alkaline earth metals. Among these valuable metal ions, ions of metals selected from Be, Sc, Y, Fe, Ru, Pd, Cu, Au, Cd, Al, Ga, In, Pb, and lanthanoid metals are preferable.

  The above valuable metal ions are obtained by crushing various samples that are thought to contain these valuable metal ions, electronic devices such as mobile phones and personal computers, or home appliances to an appropriate size, aqua regia, sulfuric acid, hydrochloric acid, nitric acid, etc. It may be prepared from a solution obtained by dissolving in an acid solution.

  The preparation of an aqueous solution containing the pH-responsive polymer and valuable metal ions and having a pH higher than 6.4 is not particularly limited. For example, the aqueous solution is prepared by adding a pH-responsive polymer and valuable metal ions to water at room temperature (about 15 to 20 ° C.), and then adjusting the pH of the aqueous solution by a pH adjustment method known in the art, such as sodium hydroxide. It can be prepared by adding an alkaline substance or an acidic substance such as hydrochloric acid to be higher than 6.4, preferably 9 to 11. The pH of the aqueous solution containing 1 to 0.4% by mass (hereinafter simply referred to as “%”), preferably 0.2 to 0.3% is the same as above, and the pH is higher than 6.4, preferably pH 9 Then, the pH-responsive polymer is stirred until it is sufficiently dissolved, and further, valuable metal ions are added to this aqueous solution to a concentration of 0.1 to 10 ppm, preferably 1 to 2 ppm. Water It can be prepared by setting the pH of the solution to be higher than 6.4, preferably 9 to 11, in the same manner as described above.

  The aqueous solution prepared above may contain alkali metals that cannot be recovered by the recovery method of the present invention, metal ions of Group 6 of the periodic table such as Cr, Mo, W, and nonmetallic elements such as Se. Good.

  Next, the aqueous solution prepared in the step (a) is adjusted to a pH of 6.4 lower than 6.4, preferably 5 to 6 in the step (b), and a pH-responsive polymer and valuable metal aggregates are formed. This pH adjustment can be performed in the same manner as described above.

  The aggregate obtained in step (b) is then recovered from the aqueous solution in step (c). A method for collecting the aggregate from the aqueous solution is not particularly limited, and a separation method known in the art can be used. Further, the conditions for this separation method are not particularly limited, and may be set as appropriate according to the generated precipitate. In the present invention, filtration using a filter medium such as a general filter paper, a hydrophilic PTFE filter, a glass fiber filter, or a glass prefilter is preferable among the separation methods, and suction filtration using the filter medium is particularly preferable.

The valuable metals can be recovered as aggregates of the pH-responsive polymer by the above steps (a) to (c). Furthermore, the following step (d)
(D) Only valuable metals can be recovered by adding an aqueous solution having a pH higher than 6.4 to the collected aggregates and performing a step of recovering valuable metals.

  Specifically, in the step (d), an aqueous solution having a pH higher than 6.4, preferably pH 12 to 13, is added to the aggregate collected in the step (c) to recover valuable metals. Since phase transition occurs in the pH-responsive polymer in the aggregate in this step (d), the pH-responsive polymer is dissolved in the aqueous solution, and valuable metals are precipitated. Examples of the aqueous solution having a pH higher than 6.4 used in this step include those described above. The method for adding the aqueous solution having a pH higher than 6.4 to the aggregate is not particularly limited. For example, after the aggregate separated in the step (c) is recovered, the aqueous solution having a pH higher than 6.4 is collected. Although the agglomerates may be immersed to recover the metal, it is preferable to pass an aqueous solution having a pH higher than 6.4 directly through the agglomerates separated on the filter medium in the step (c). By doing so, valuable metals are recovered on the filter medium, and pH-responsive polymer is recovered in the filtrate.

  Furthermore, since the aqueous solution after recovering the valuable metal in the step (d) contains a pH-responsive polymer, the pH is lower than 6.4, preferably 5 to 6, and aggregates due to phase transition. The pH responsive polymer can be recovered. The pH of this aqueous solution can be adjusted in the same manner as described above. Further, the pH-responsive polymer recovered here can be reused for the recovery method of the present invention and other applications.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples at all.

Each characteristic in the examples was analyzed according to the following method.
(1) Weight average molecular weight, number average molecular weight and molecular weight distribution of pH responsive polymer The weight average molecular weight, number average molecular weight and molecular weight distribution of the pH responsive polymer are determined by poly (4- [2- (vinyloxy)- Ethoxy] -ethyl benzoate) was estimated from the weight average molecular weight, number average molecular weight and molecular weight distribution. The weight average molecular weight, number average molecular weight and molecular weight distribution of poly (4- [2- (vinyloxy) -ethoxy] -ethyl benzoate) were measured by gel permeation chromatography (GPC) using the following RI detector. Obtained from the calibration curve.
GPC device: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: KF804L (manufactured by Shodex) x 3 Eluent: Tetrahydrofuran (2) Measurement of metal concentration The concentration of metal ions was measured using an ICP emission spectrophotometer (OPTI-MA3300DV type: manufactured by Perkin-Elmer).
(3) Measurement of absorbance The absorbance was measured using a spectrophotometer (V-570 spectrophotometer: manufactured by JASCO Corporation).
(4) Measurement of pH The pH was measured using a pH meter (F-51: manufactured by HORIBA).
(5) Measurement of NMR NMR was measured using JEOL-AL400 made by JEOL.

Reference example 1
Synthesis of 1-butoxyethyl acetate (IBEA):
To a 500 mL three-necked flask, 272 g (2.72 mol) of isobutyl vinyl ether (manufactured by Tokyo Chemical Industry) and 120.4 g (2.00 mol) of acetic acid (manufactured by WAKO) were added and stirred at 60 ° C. for 24 hours. After completion of the reaction, 1-butoxyethyl acetate was obtained by adding calcium hydride to the resulting liquid and purifying it by distillation.

Reference example 2
Synthesis of ethyl 4- (vinyloxyethoxy) benzoate (VEBAE):
To a 1 L three-necked flask, 100 g (0.60 mol) of ethyl 4-hydroxybenzoate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 150 g (1.09 mol) of potassium carbonate (manufactured by WAKO) were added, and 60 ° C. in N-methylpyrrolidone solvent. Then, 77 g (0.72 mol) of chloroethyl vinyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise using a dropping funnel. Next, the temperature was raised to 100 ° C. and reacted for 24 hours.

  The obtained reaction solution was diluted with water, extracted with ethyl acetate, and the solvent was distilled off to obtain crude crystals of ethyl 4- (vinyloxyethoxy) benzoate. Further, the obtained crude crystals were dissolved in toluene, washed with water, and the solvent was distilled off. Then, the crude crystals were dissolved in hexane and recrystallized to obtain needles of ethyl 4- (vinyloxyethoxy) benzoate. Crystals were obtained. The yield was 108 g (68% yield).

Reference example 3
Synthesis of poly (4- [2- (vinyloxy) -ethoxy] -benzoic acid):
A 500 ml three-necked flask was charged with 62 g (0.85 M) of ethyl 4- (vinyloxyethoxy) benzoate (VEBAE), followed by vacuum drying and argon substitution three times. Next, 300 ml of toluene, 0.09 ml (2 mM) of 1-butoxyethyl acetate (IBEA) and 30 ml (1 M) of ethyl acetate as starting species were added, and the mixture was stirred at 0 ° C. for 30 minutes under argon substitution. Thereafter, 3 ml (5 mM) of 0.5 M tin (IV) chloride as an activating agent was added thereto, and the mixture was reacted by stirring at 0 ° C. for 1 hour under argon substitution. Finally, 12 ml of methanol was added thereto, and the reaction was stopped to obtain a polymer solution.

  To the polymer solution obtained above, 2.5% activated alumina was added and stirred, followed by filtration using 5C filter paper manufactured by Advantech. Toluene was distilled off from the filtrate under reduced pressure to obtain 55.1 g (yield: 88.9%) of an elastic brown solid. The weight average molecular weight, number average molecular weight, and molecular weight distribution of this poly (4- [2- (vinyloxy) -ethoxy] -ethyl benzoate) were 21,400, 14,700, and 1.45, respectively.

  Next, 600 g of the polymer, dimethyl sulfoxide, and 600 g of 5M aqueous sodium hydroxide solution were charged into a 1 L eggplant-shaped flask and stirred at 100 ° C. for 20 hours. The obtained reaction solution was diluted with water, and diluted and precipitated with a 5M aqueous hydrochloric acid solution to obtain crude poly (4- (vinyloxyethoxy) benzoic acid). The polymer was washed with ion-exchanged water and vacuum-dried (80 ° C., 4 nights) to obtain 46.8 g (yield 84%) of a white solid.

また、このＰｏｌｙ（ＶＥＢＡ）ｓの溶液特性を調べたところ、ｐＨ６.４付近で相転移を起こすことがわかった。 As a result of carrying out NMR measurement about the brown solid obtained above, it turned out that it is a polymer (Poly (VEBA) s) which has the following formula (I) as a structural unit (FIG. 1 and FIG. 2).

Further, when the solution characteristics of this Poly (VEBA) s were examined, it was found that a phase transition occurred around pH 6.4.

Example 1
Metal recovery (1):
In a 50 ml sample tube, 0.04 g of Poly (VEBA) s synthesized in Reference Example 1 and 2 ml of a 0.1 M sodium hydroxide aqueous solution were placed, and the poly (with a shaker (MULTI SHAKER-MMs-300: manufactured by Tokyo Rika Kikai Co., Ltd.)) VEBA) s were stirred until completely dissolved. The pH of this solution was 9. Next, metal ions shown in Table 1 were added thereto at a concentration of 1 ppm, and then the pH was adjusted to 5.5 with a nitric acid solution to form poly (VEBA) s and metal aggregates. Further, this solution was filtered by suction filtration using a PTFE filter as a filter medium, and aggregates were collected on the PTFE filter. The metal concentration in the filtrate was measured, and the metal recovery rate was calculated therefrom. The results are also shown in Table 1.

  From the above, Poly (VEBA) s is Be, Sr, Ba, Sc, Y, Ti, Zr, Nb, Ta, Mn, Fe, Ru, Co, Ni, Pd, Cu, Au, Zn, Cd, Hg, A metal ion selected from Al, Ga, In, Pb, Bi and a lanthanoid metal (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) is preferably used. It was found that ions of metals selected from Be, Sc, Y, Fe, Ru, Pd, Cu, Au, Cd, Al, Ga, In, Pb and lanthanoid metals can be recovered. .

Example 2
Metal recovery (2):
In a 50 ml sample tube, 0.04 g of Poly (VEBA) s synthesized in Reference Example 1 and 2 ml of a 0.1 M sodium hydroxide aqueous solution were placed, and stirred with a shaker until the Poly (VEBA) s was completely dissolved. The pH of this solution was 9. Next, 14 kinds of lanthanoids (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) metal ions are added at a concentration of 1 ppm each, and then The pH was adjusted to 5.5 with a nitric acid solution to form poly (VEBA) s and metal aggregates. Further, this solution was filtered by suction filtration using a PTFE filter as a filter medium, and aggregates were collected on the PTFE filter. Further, the recovery rate of 14 lanthanoid metals was calculated in the same manner as in Example 1. As a result, all of the lanthanoid metals were in a state where 14 kinds were mixed, and the recovery rate was 100%.

Example 3
Metal recovery (3):
In Example 2, except that 14 kinds of lanthanoid metal ions and metal (Cr, W, Rh, Ag, Ge) ions that did not show phase transition in Example 1 were added at a concentration of 1 ppm, respectively. The metal was recovered in the same manner as 2 and the recovery rate was calculated. As a result, even when a metal that did not exhibit a phase transition was mixed with a metal that had undergone a phase transition, all the lanthanoid metals had a recovery rate of 100%.

Example 4
Metal recovery (4):
In Example 2, instead of the PTFE (polytetrafluoroethylene) filter (pore size 1.0 μm) used as the filter medium, a PTFE filter (pore size 0.2 μm), a glass fiber filter (pore size 1.0 μm), and a cellulose-containing filter (pore size) The recovery rate of the lanthanoid metal was calculated in the same manner as in Example 2 except that 0.2 μm). As a result, the recovery rate of the lanthanoid metal was 100% in any filter.

Example 5
Metal recovery and polymer reuse:
The agglomerates separated and collected on the PTFE filter in the same manner as in Example 2 were further subjected to suction filtration while adding a 1.0 M sodium hydroxide solution. After suction filtration, metal remained on the filter. This is considered to be because Poly (VEBA) s in the aggregate undergoes phase transition by adding a sodium hydroxide solution to the aggregate, dissolves in the filtrate, and passes through the filter. Further, after suction filtration, the recovery rate of the lanthanoid metal calculated in the same manner as in Example 2 was 100%.

  Further, the pH of the filtrate obtained after the suction filtration was set to 5.5 with a nitric acid solution, and Poly (VEBA) s was phase-aggregated and aggregated, and then the absorbance of the filtrate was measured. Next, this filtrate was filtered with a PTFE filter to collect Poly (VEBA) s. When the absorbance of the filtrate after recovery of Poly (VEBA) s was measured, the spectrum observed in the filtrate after phase transition and aggregation of Poly (VEBA) s was not completely observed (FIG. 3). . This indicates that Poly (VEBA) s can be recovered 100% by this operation and can be reused.

  The method for recovering valuable metals according to the present invention can recover valuable metals with good selectivity from electronic devices such as mobile phones and personal computers, or home appliances.

Therefore, the valuable metal recovery method of the present invention can contribute to the reuse of metal resources.

more than

Claims (7)

The following steps (a) to (c),
(A) The following formula (I)

A pH-responsive polymer having a structural unit and a valuable metal ion, and the pH is 6
A step of preparing an aqueous solution higher than .4 (b) a step of lowering the pH of the aqueous solution below 6.4 to form an aggregate of a pH-responsive polymer and valuable metals (c) a step of recovering the aggregate from the aqueous solution A method for recovering valuable metals, comprising:   The method for recovering valuable metals according to claim 1, wherein the valuable metal ions are ions of a metal selected from heavy metals and light metals.   Heavy metal selected from the group consisting of Ti, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Ru, Pd, Cd, In, Ta, Au, Hg, Pb, Bi and lanthanoid metals The method for recovering valuable metals according to claim 2.   The method for recovering a valuable metal according to claim 2, wherein the light metal is selected from the group consisting of Sc, Al and alkaline earth metals.   2. The valuable metal ion according to claim 1, wherein the valuable metal ion is an ion of a metal selected from the group consisting of Be, Sc, Y, Ga, In, Au, Ru, Pd, Pb, Cd, Cu, Al, Fe, and a lanthanoid metal. Metal recovery method. Furthermore, step (d)
(D) The method for recovering valuable metals according to any one of claims 1 to 5, comprising a step of adding an aqueous solution having a pH higher than 6.4 to the collected aggregates and recovering the valuable metals. The method for recovering a valuable metal according to claim 6, wherein in step (d), the pH of the aqueous solution after recovering the valuable metal is lowered to less than 6.4 to recover the pH-responsive polymer.

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