JPH06212309A - Method for recovering rare-earth elements by selective adsorption - Google Patents

Abstract

PURPOSE:To separate rare-earth ions from an aq. soln. of the mixture of rare- earth ions and base-metal ions by selective adsorption by adding chlorella, spirulina or a water-soluble component obtained by leaching spirulina with water at specified pH and separating the leachate from liq. to an aq. rare-earth ion soln. and specifying the pH. CONSTITUTION:Chlorella, spirulina or a water-soluble component obtained by leaching spirulina with water at pH 5-7 and separating the leachate from liq. is added to an aq. rare-earth ion soln., and the pH is controlled to 3-4.5. When spirulina or chlorella is used as the adsorbent, the adsorptivity to the rare-earth elements is maximized at pH 3-4.5. The adsorptivity of spirulina or chlorella to base metals such as copper and cobalt is low at pH 3-4.5. Accordingly, the rare-earth ions are selectively adsorbed and separated from an aq. mixed soln. of the base-metal ions and rare-earth ions at pH 3-4.5.

Description

Description: [Industrial application] [0001] The present invention relates to a method for adsorbing metal ions in an aqueous solution using algal powder,
The present invention relates to a method for selectively adsorbing and collecting rare earth ions, which can be used for separating and collecting rare earth ions from a mixed aqueous solution of rare earth ions and other metal ions.

[Prior Art] [0002] A conventional report on the action of a method for adsorbing metal ions present in an aqueous solution using algae includes a simple adsorption action similar to that of activated carbon, a cation. There are a cation exchange action similar to an exchange resin and an anion exchange action similar to an anion exchange resin. The metal ions that are adsorbed based on the cation exchange action are the majority of cation-type metal ions such as copper ions, cobalt ions, and cadmium ions. The metal ions that are adsorbed on the basis of the anion exchange action are anions such as chloroaurate ion and chloroplatinate ion.

[Problems to be Solved by the Invention] [0003] Needless to say, if a cation-exchangeable adsorbent is used, cations are adsorbed at a high rate at a pH close to neutral and the anion adsorption rate is low. Becomes On the contrary, when an anion exchange adsorbent is used, the anions are adsorbed at a high rate and the cations are adsorbed at a low rate in weakly acidic conditions. Therefore, selective adsorption separation from a mixed aqueous solution of a metal cation and a metal anion is relatively easily realized by using any of the cation-anion exchange adsorbents at a suitable pH. However, selective adsorption separation of metal cations or metal anions is impossible in principle. Since rare earths such as samarium, neodymium, yttrium, or lanthanum and base metals such as copper, cobalt, or iron also exist as cations in ordinary aqueous solutions, selective adsorption separation of rare earths and these base metals cannot be easily performed. .

[0004] When rare earths are used industrially, they are often used in admixture with base metals, such as in the case of samarium and cobalt. Therefore, in order to recycle and use industrially used rare earths, it is necessary to establish a technique for separating rare earths and base metals. The present invention is
The present invention relates to a method for selectively adsorbing and separating rare earth ions from a mixed aqueous solution of rare earth ions and base metal ions.

[Means for Solving the Problem] [0005] The present inventors first conducted an experiment of adsorbing a rare earth ion aqueous solution with various algal powders. The results are shown in FIGS. This is the case where samarium, neodymium, yttrium, and lanthanum chloride aqueous solutions were used as test liquids in the order of FIGS. According to these, when konbu or wakame is used as algae, the adsorption rate of rare earth ions is high in the vicinity of neutrality and low in weak acidity. Moreover, when a cation exchange resin is used, a high adsorption rate is exhibited regardless of the pH. Therefore, it is considered that rare earth ions are adsorbed by cation exchange reaction. On the other hand, base metals such as copper and cobalt are also adsorbed by algae in a cation exchange reaction as described above. Therefore, when Konbu, Wakame or ion-exchange resin is used, selective adsorption separation of rare earth and copper or cobalt cannot be performed.

[0006] However, when Spirulina or Chlorella is used as the adsorbent, the adsorption rate of the rare earth element exhibits the highest value at pH 3 to 4.5, as can be seen from FIGS. The adsorption rate of base metals such as copper and cobalt by Spirulina or chlorella at pH 3 to 4.5 is low.
Therefore, selective adsorption and separation of rare earth ions from the mixed aqueous solution of these base metal ions and rare earth ions was possible at pH 3 to 4.5. The phenomenon that the adsorption rate shows the maximum value at pH 3 to 4.5 was considered to be due to a special mechanism in which the adsorption reaction was neither a cation exchange reaction nor an anion exchange reaction. Therefore, the inventors further conducted the experiment by paying attention to the color of the aqueous solution when spirulina was used. Figure 5
As shown in Fig. 5, the pigment of spirulina is extracted by water having a pH around neutrality, and the aqueous solution exhibits a beautiful dark blue color. On the other hand, when Spirulina was brought into contact with weakly acidic water having a pH of 1 to 2, the aqueous solution showed a pale blue color. However, pH3
The color of the aqueous solution when spirulina was brought into contact with water of ˜4.5 became colorless. From the above experiments, it was estimated that the spirulina pigment aggregates at pH 3 to 4.5, and the rare earth ions are adsorbed and collected by the aggregated pigment.

[0007] Next, in order to confirm this estimation, spirulina was extracted with water having a pH of around 6, the residue was removed by filtration, and the resulting aqueous dye solution was freeze-dried to obtain various powders with various pH values as adsorbents. 6 shows the adsorption rate when the rare earth ion was adsorbed from the aqueous solution thereof, and FIG. 7 shows a photograph of the filtrate and the residue of the filter paper when the slurry after the adsorption reaction was filtered by the filter paper. FIG. 7 shows the case where samarium is used as the rare earth element, but the similar tendency was observed in the case of other rare earth elements. In addition, the color tone and the degree of aggregation of the dye did not change regardless of the presence or absence of metal ions in the test aqueous solution, and depended only on the pH. According to FIG. 7, a pH of 3 to
Only in the case of 4.5, the filter paper is colorless and the filter paper residue is blue, and in the case of other pH, the filter solution is blue and the filter paper residue is colorless or light blue. Aggregation of the blue dye at 4.5 was confirmed. According to FIG. 6, it is clear that the rare earth ions are adsorbed to this aggregated dye at a very high rate, and at a pH at which the dye is not aggregated,
Rare earth ions remain in the aqueous solution. After all, the tendency of the rare earth adsorption rate in FIG. 6 to change with pH is sharper than in FIG. 1, and it was confirmed that the rare earth ion adsorption action by spirulina is extremely deeply related to the aggregation phenomenon of the blue dye in a specific pH range. It was

[0008] Next, FIG. 8 shows the experimental results when the adsorbed ions were copper or cobalt under the same conditions as in FIG. Figure 8
According to the above, it was confirmed that copper or cobalt was hardly adsorbed by the aggregated blue dye having a pH of 3 to 4.5. Therefore,
It is understood that selective adsorption separation of rare earths is possible with aggregated blue dyes. FIGS. 6 and 8 show the experimental data when a lyophilized water extract from spirulina was used as an adsorbent. The spirulina water extract was added to the metal ion-containing aqueous solution as it was without being lyophilized. The same effect was obtained when the value was adjusted. In addition, the adsorption rate of rare earth, copper or cobalt to the filtration residue obtained by eluting the water-soluble blue dye or the like from Spirulina at pH 6 to 7 is shown in Fig. 9. According to this, the adsorption rate of rare earth depends on the pH.
No peaks of 3 to 4.5 are observed. Therefore, it is judged that the adsorption of the rare earth at pH 3 to 4.5 by Spirulina is due to the action of the aggregating dye.

[0009] In summary, in the constitution of the present invention, the water-soluble component obtained by leaching solid-liquid separation of chlorella, spirulina or spirulina with water having a pH of 5 to 7 is added to the rare earth ion aqueous solution to adjust the pH to 3 to. It is a selective adsorption recovery method for rare earths, which is characterized in that the insoluble residue is adsorbed with the rare earths adjusted to 4.5.

[Operation] [0010] As described above and as can be seen from the following examples, it is understood that the aggregated blue pigment of Spirulina has a high selective adsorption property to rare earth ions. The blue pigment extracted with water from Spirulina is said to be phycocyanin. Figure 1
1 shows the structural formula of phycocyanin. Lactose or trisodium citrate is added to and mixed with phycocyanin to stabilize it, and the product is commercialized and called Lina Blue A, which is used as a blue colorant for frozen desserts and the like. When the adsorption behavior of this rare earth to Linablue A was investigated by experiments, it showed the highest value at pH 3 to 4.5, but the adsorption rate was generally low, and the amount of Linablue A used was increased to increase the net amount of phycocyanin charged. Since the adsorption rate of rare earth did not improve even when the values were equal, it was estimated that the mixed components interfered with the adsorption action. There is no report on the fact that the selective adsorption of rare earth ions occurs when the aqueous phycocyanin solution aggregates at pH 3 to 4.5. Regarding the mechanism of metal ion adsorption by algae, although many are based on the cation or anion exchange action, there is no report showing the metal ion selective adsorption action associated with the dye aggregation action in a specific pH range. Examples will be shown below, but the present invention is not limited thereto.

[Example] (Example 1) [0011] Samarium concentration 12 mg / l
20m samarium chloride aqueous solution whose concentration is adjusted to
agar powder with stirring in a beaker at room temperature.
0 mg was added, and if necessary, a very small amount of hydrochloric acid was dropped so as to obtain a predetermined pH, and the mixture was stirred for 1 hour. FIG. 1 shows the adsorption rate from the samarium concentration in the aqueous solution before and after the treatment, and shows the results for each alga in comparison with pH. FIG. 2 shows a similar experimental result in which the adsorbed ions were Neodymium, FIG. 3 shows a result of yttrium, and FIG. 4 shows a result of lanthanum. In each figure, it is clearly seen that when Spirulina and Chlorella are used as algae, the maximum adsorption rate of rare earth ions is at pH 3 to 4.5.

(Example 2) [0012] 60 mg of spirulina powder was added to 20 ml of water with stirring, and the pH was dropped by adding hydrochloric acid.
FIG. 5 is a photograph of the filtered filtrate of the slurry adjusted to 1, 2, 3, 4, 5, 6, 6 and 7, and photographed the color thereof. It can be seen that the pH liquor at pH 7 to 6 exhibits a deep blue color, but it becomes almost colorless at pH 3 to 4.5, and becomes a bluish liquor again at pH 2 or 1.

(Example 3) [0013] When 6 g of spirulina powder was slurried with 120 ml of distilled water, the pH was 6.79. 2.7 g of the filtration residue was removed by filtration by filtration. When the blue aqueous solution obtained by this operation was freeze-dried, 1.2 g of blue powder was obtained. 30 mg of each of the blue powders was added to 20 ml of a chloride aqueous solution containing samarium, neodymium, yttrium or lanthanum with a concentration of 12 mg / l, the pH was adjusted by adding a very small amount of hydrochloric acid while stirring, and the mixture was filtered for 1 hour after filtration. Solid-liquid separation was carried out with and the adsorption rate was calculated from the rare earth ion concentrations in the liquid before and after the treatment. The results are shown in FIG. 6 as a graph of pH and adsorption rate. According to this result, p as in FIGS.
The adsorption rate of rare earth ions is maximum in H3 to 4.5. Each p when samarium is used as a rare earth
A photograph of the filtrate and the filtration residue after the adsorption stirring treatment in H is shown in FIG. According to this, in the vicinity of pH 6, the blue dye does not aggregate at all, and therefore the rare earth ions also remain in the aqueous solution. When the pH is around 2, only a slight amount of blue pigment remains on the filter paper, but the filtrate has a considerably blue color, and the samarium ion remains in the aqueous solution. Contrary to this, pH 3-4.
In the case of 5, a considerable amount of the aggregated blue dye remains on the filter paper, the filtrate becomes colorless, and most of the samarium ions remain in the aggregated blue dye. In the case of other rare earths other than samarium, the relationship between the pH and the color tone of the filtrate and the filtration residue was similar.

(Example 4) [0014] FIG. 8 shows the relationship between pH and adsorption rate when the ions to be adsorbed were copper or cobalt under the same conditions as in FIG. In this case, the relationship between the pH and the color tones of the filtrate and the filtration residue was exactly the same as in FIG. According to FIG. 8, pH 2 and 6 at which blue dye hardly remains on the filter paper
It can be understood that copper and cobalt are all left in the filtrate when the pH is 3 to 4.5 where the blue dye remarkably remains on the filter paper in the vicinity.

(Example 5) [0015] A filtration residue 60 m in which a water-soluble blue dye or the like was eluted from Spirulina at pH 6 to 7.
g was added to each ion-containing aqueous solution, and other conditions are shown in FIG.
FIG. 9 shows the adsorption rates of rare earth elements, copper or cobalt in the same experiment. According to this, the peak of pH 3 to 4.5 is not observed in the adsorption rate of rare earth.

(Example 6) [0016] Spirulina or chlorella was added to a mixed chloride aqueous solution prepared so that each of samarium and cobalt ions was present at 12 mg / l, and an adsorption experiment was conducted under the same conditions as in FIG. Show.
It can be seen that samarium is well selectively adsorbed to cobalt ions at pH 3 to 4.5.

EFFECTS OF THE INVENTION [0017] According to the present invention, it is possible to supply a method for selectively adsorbing rare earth ions at pH 3 to 4.5 and an adsorbent therefor, which is considered to be particularly useful for utilization of rare earth recycling resources.

[Brief description of drawings]

1, 2, 3, and 4 are graphs showing the adsorption rates of samarium, neodymium, yttrium, and lanthanum ions by various algae in comparison with the horizontal axis of pH. FIG. 5 is a photograph showing the pH and the color of the filtrate when spirulina was slurried with water. FIG. 6 is a graph showing the adsorption rate of rare earth ions by the blue pigment extracted with water from Spirulina in comparison with the horizontal axis of pH. FIG. 7 is a photograph showing the colors of the filtrate and the residue of the paper filter after the samarium ion was adsorbed at each pH by the spirulina blue dye and then filtered. FIG. 8 is a graph showing the adsorption rate of copper or cobalt ions by the Spirulina blue dye in comparison with the horizontal axis of pH. FIG. 9 is a graph showing the adsorption rate of rare earth, copper or cobalt ions by the filtration residue obtained by eluting a water-soluble component such as blue pigment from Spirulina, in comparison with the horizontal axis of pH. FIG. 10 shows the results of the selective adsorption experiment of samarium from a mixed chloride aqueous solution of samarium and cobalt by Spirulina or Chlorella. FIG. 11 is a structural formula of phycocyanin. The symbols of adsorbents such as algae in each figure are as follows. CV ... Chlorella SP ... Spirulina UN ... Wakame LS ... Konbu AX ... Anion exchange resin (Organo, CG-400
I) CX ... Cation exchange resin (Organo, CG-120)
I)

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[Procedure amendment]

[Submission date] December 10, 1993

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[Brief description of drawings]

FIG. 1 is a graph showing the adsorption rate of samarium by each alga.

FIG. 2 is a graph showing the adsorption rate of neodymium by each alga.

FIG. 3 is a graph showing the adsorption rate of yttrium by each alga.

FIG. 4 is a graph showing the adsorption rate of lanthanum by each alga.

FIG. 5 shows the pH when spirulina is slurried with water.
And shows the blue color of the filtrate. The numbers in the lower part of the figure represent pH, and the density of the diagonal lines represents the blue density of the filtrate.

FIG. 6 is a graph showing the adsorption rate of rare earth ions by a blue pigment extracted with water from Spirulina in comparison with the horizontal axis of pH.

FIG. 7 shows the blue strength of the filtrate and the residue of the filter paper of samarium ion adsorbed by Spirulina blue dye at each pH. The numbers in the lower part of the figure indicate pH, and the density of each hatched line indicates the dark blue color of the filtrate or filter paper residue.

FIG. 8 is a graph showing the adsorption rate of copper or cobalt ions by Spirulina blue dye in comparison with the horizontal axis of pH.

FIG. 9 is a graph showing the adsorption rate of rare earth, copper or cobalt ions by a filtration residue obtained by eluting a water-soluble component such as blue pigment from Spirulina, in comparison with the horizontal axis of pH.

FIG. 10 shows the results of a selective adsorption experiment of samarium from a mixed chloride aqueous solution of samarium and cobalt by Spirulina or Chlorella.

FIG. 11 is a structural formula of phycocyanin. The symbols of adsorbents such as algae in each figure are as follows. CV ... Chlorella SP ... Spirulina UN ... Wakame LS ... Konbu AXR ... Anion exchange resin (Organo, CG-400
I) CXR ... Cation exchange resin (Organo, CG-120)
I)

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Claims (1)

[Claims] [Claim 1] A water-soluble component obtained by leaching solid-liquid separation of chlorella, spirulina or spirulina with water having a pH of 5 to 7 is added to a rare earth ion aqueous solution to adjust the pH to 3 to.
A method for selectively adsorbing and recovering rare earths, which comprises adjusting to 4.5 and adsorbing rare earths on an insoluble residue.