JP2000192167A - Method for selecting and seprating rare metal component from waste fluorescent material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further facilitate the separation and recovery of rare metal components from disposed waste fluorescent lamps containing various kinds of rare metals. SOLUTION: Waste fluorescent materials containing rare metal components are subjected to the mechano-chemical treatment of low degree to elude Y and Eu components in a weak acid, and then subjected to the mechano-chemical treatment of high degree to elude La, Ce and Tb components in a weak acid to selectively separate the rare metal components. The degree of the mechano- chemical treatment includes the rotational speed and the treatment time by a ball mill, and in a specific example, the combination of the rotational speed of 700 rpm for two treatment hours by the ball mill is of high degree, while the combination of the rotational speed of 400 rpm for 20 minutes is of low degree. Hydrochloric acid or sulfonic acid of <=1N is suitable for the weak acid. Since the rare metal components can be extracted by the kind in two parts, the final separation of each component is easy to enable the cyclic use of rare resources.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating fluorescent lamps containing various rare metals from abandoned fluorescent tubes by type.

[0002]

2. Description of the Related Art Rare metals (rare earth elements) have atomic number 5
Sc with similar chemical properties to 15 elements from La (lanthanum) 7 to Lu (lutetium) with atomic number 71
(Scandium) and Y (yttrium), which is a collective term for 17 elements including three elements, such as a three-wavelength fluorescent tube, a catalyst,
It is an important element indispensable for the production of so-called functional materials such as optical glass, fine ceramics and magnets. And these elements are usually high temperature starting from ores such as monazite, bastnaesite and xenotime,
At present, it is manufactured by an extraction operation using a high-concentration acid.

An enormous amount of rare metal ore is required in order to meet the increasing demand for rare metal, but the rare metal-containing ore is produced mainly in China, North America, Russia, etc. all over the world. Therefore, relying solely on the acquisition of rare metals may lead to exhaustion sooner or later. As described above, there is a limit in relying only on ore for resources, and a method of recovering rare metals from waste is desired as a future technology.

As a promising rare metal recovery target, a three-wavelength high color rendering fluorescent tube that is discarded in large quantities is expected. In other words, rare metals are widely used as fluorescent materials for three-wavelength high color rendering fluorescent tubes, and as the demand for fluorescent tubes using them increases year by year, the amount of used and discarded fluorescent tubes continues to increase. Therefore, it is considered that rare metals are separated and collected from the fluorescent tubes to be discarded and reused. Fluorescent materials used for fluorescent tubes include Y,
Many rare metals such as La, Eu, Ce, and Tb are included. Since the conventional recovery technique is an extraction method using a high-temperature, high-concentration acid, there is a problem in the working environment, and establishment of a recovery method under milder conditions has been desired.

The present inventor has positioned waste fluorescent lamps as a promising rare metal city resource in the future, and previously combined mechanochemical treatment with extraction using a weakly acidic solution at room temperature, and under more mild conditions. As a result of exploring the possibility of extracting rare metals from waste fluorescent tubes, dry mechanochemical treatment was applied to these discarded fluorescent materials, and if rare metal leaching was performed at room temperature with a weak acid,
It has been found that all kinds of rare metals contained dissolve in acids in high yield.

[0006]

SUMMARY OF THE INVENTION The present invention aims to provide a method for separating these types of waste fluorescent tubes from waste fluorescent tubes containing various rare metals, in order to further facilitate their separation and recovery. .

[0007]

Here, the present inventor has performed a low-level mechanochemical treatment on a waste fluorescent material containing a rare metal component to obtain Y and Eu.
We have found a method for selectively separating rare metal components from waste fluorescent material, characterized in that components are eluted in a weak acid and a high degree of mechanochemical treatment is applied later to elute La, Ce, and Tb components in a weak acid. .

The degree of the mechanochemical treatment depends on the rotation speed of the ball mill and the processing time. As a specific example, the rotation speed of the ball mill is 700 rpm.
Thus, the combination of 20 minutes at 400 rpm for the two-hour process can be made larger or smaller. The weak acid used for eluting the rare metal component is preferably hydrochloric acid or sulfuric acid having a concentration of 1N or less.

[0009]

DETAILED DESCRIPTION OF THE INVENTION A mechanochemical is generally defined as a mechanical energy added to a solid substance, for example, shear, compression, impact, crushing, bending or stretching, and the like, which causes a physicochemical change in the surface of the solid. Known as a phenomenon that affects a chemical state by causing a chemical change to a gas or liquid substance present in the water, or by directly inducing or promoting a chemical change between them and a solid surface. .

When removing the rare metal component from the waste fluorescent tube, it is necessary to remove the mercury component in the metal fittings and the tube in advance, crush the whole, and mechanically separate the rare metal component, and then subject it to dry mechanochemical treatment. desirable. In the case of a normal fluorescent tube, when it is folded in half, a part of the fluorescent material is peeled off, and some glass fragments are accompanied. Further, when vibration is applied to the broken fluorescent tube, 95% or more of the fluorescent material is peeled off. When this is sieved through, for example, a 200-mesh sieve (aperture 74 microns), almost 70% of the supplied fluorescent material is recovered, and the glass component is separated. However, it has been found that the waste fluorescent material obtained here has deteriorated and cannot be reused as a fluorescent material as it is. It is presumed that this is probably due to the fact that it is not a solid solution as an oxide, that is, it has just changed to a mixture of oxides. In addition, since the fluorescent material obtained in this way cannot avoid the accompanying glass component, it was found that the effect in that case was examined, and it was found that the effect of the dry-type mechanochemical treatment was improved when the glass component was large. . Therefore,
The waste fluorescent material containing a rare metal component in the present invention includes a case where a glass component coexists.

[0011]

The present invention will be described below in detail with reference to examples. [Fluorescent material] The fluorescent material contained in the three-wavelength high color rendering fluorescent tube to be discarded (hereinafter simply referred to as a fluorescent material) is a powder in which blue, green, and red monochromatic phosphors are mixed. It is composed of a composite oxide. Blue phosphor: BaMgAl ₁₀ O ₁₇ : Eu ²⁺ (abbreviation:
BAT) Green phosphor: LaPO ₄ : Ce ³⁺ , Tb ³⁺ (abbreviation:
LAP) Green phosphor: CeMgAl ₁₁ O ₁₉ : Tb ³⁺ (abbreviation:
MAT) Red phosphor ・ ・ ・ Y ₂ O ₃ : Eu ³⁺ (abbreviation: YOX)

[Dry Mechanochemical Treatment] As a high energy type pulverizer in dry mechanochemical treatment of fluorescent material (hereinafter referred to as mechanochemical treatment), a planetary ball mill (Planetary Mi, manufactured by Fritsch) is used.
cro Ball, Pulverisset-7) was used. This planetary ball mill is composed of two zirconia mill pots having a capacity of 50 cm ³ attached to a rotating disk with a clockwise rotation of 70 mm and a turning radius of 70 mm. It can rotate at the same speed as the disk. The mill pot contains 7 balls made of zirconia having a diameter of 15 mm and phosphor powder 5.
g was loaded, the mill rotation speed was changed, and mechanochemical treatment was performed for a predetermined time. Grinding is carried out by the batch method,
All the products obtained by processing for a predetermined time were collected. The longest processing time was 2 hours. In particular, in order to avoid excessive heat generation in the pot, the operation of stopping for 30 minutes after the 15-minute operation and repeating the natural cooling operation was repeated. The product after each milling time is
Particle size distribution measurement (Seisin, Laser Micro
nSizer, LMS-30), X-ray diffraction (XRD)
(Rigaku, RAD-Bsystem, Cu-K
α), thermal analysis (Rigaku, TAS-200) and the like were performed to evaluate changes in powder characteristics due to mechanochemical treatment.

FIG. 1 shows four types of monochromatic phosphors and the
The XRD pattern of mechanochemically treated for 0 minute (upper and lower, respectively) is shown. It can be seen from the figure that the stability of the crystal structures of these samples with respect to the mechanochemical treatment is different.

FIG. 2 shows the change in the yield of Y depending on the ball mill processing time when the rotation speed of the ball mill is changed. As shown in the figure, the yield of Y becomes better as the rotation speed of the ball mill is higher and the processing time is longer.

Particularly, when the rotation speed of the ball mill is 400 r
pm or more, the yield of Y becomes good.
Changes in the yield of each rare metal were examined under a constant condition of 00 rpm, and the results are shown in FIG. As shown in the figure, the yields of Y and Eu sharply increase with the elapse of the processing time by the ball mill, but the yields of La, Ce and Tb are increased up to about 5 to 10 minutes by the ball mill. It is low and gradually increases thereafter.

Therefore, for example, La, Ce, Tb
Is suppressed to about 10%, and the yields of Y and Eu are reduced to 80 to 80%.
To achieve 90%, use a ball with a diameter of 15 mm.
It can be seen that the rotation speed of the mill should be 400 rpm and the processing time should be set to about 20 minutes.

From these figures, the change in the yield ratio between the rare metals can be determined. For example, based on La, FIGS. 3 and 4 are obtained. From the figure, the yield ratio (R
It can be seen that e / La) (Re: Y, Ce, Tb, Eu) changes greatly at the beginning of the ball milling time and becomes constant over time.

On the other hand, FIG. 5 is obtained from FIG.
The yield ratio (Y / La) showing the acid leaching property of the fluorescent material subjected to the mechanochemical treatment is determined not only by the ball milling time but also by the ball milling time.
It can be seen that it changes depending on the rotational speed of the mill. That is, after extracting Y and Eu, the diameter of the ball is 15 m.
m, the rotation speed of the ball mill is set to 700 rpm,
If the ball mill processing time is set to about 120 minutes, La,
Ce and Tb are extracted.

[Acid Treatment] In extracting a rare metal component from a fluorescent material obtained by mechanochemical treatment, 1N hydrochloric acid was used as a low-concentration acid. 0.5 g of phosphor powder treated with mechanochemical treatment was added to 25 ml of the acid solution (weight ratio of solid / liquid = 1/50), and the mixture was stirred with a magnetic stirrer at room temperature for 1 hour.
The solution was filtered through 5C to separate the solid and the liquid.
While analyzing with P, the solid residue was identified and evaluated for its constituent components by the XRD method. In addition, acid leaching was similarly performed on the fluorescent material powder that had not been subjected to the mechanochemical treatment, and a similar analysis was performed. However, almost no acid leaching was observed.

FIG. 6 shows the XRD pattern in the case where the mechanochemical treatment was performed for 2 hours at a ball mill rotation speed of 700 rpm with respect to the fluorescent material in which the mixing ratio of the glass shards was changed. From the figure, the diffraction peaks of BAT and YOX are clear in the case where glass shards are not included (0% display), but the peaks of BAT and YOX are lower in the mixed powder in which glass shards coexist. Or disappeared. However, in the case of the fluorescent material containing glass fragments, the change in the XRD pattern depending on the content is small.

FIG. 7 shows the rotation speed of the ball mill at 700 rpm.
1 shows the effect of the glass (silica) fragment addition ratio on the leaching of rare metal components from a fluorescent material by 1N hydrochloric acid for 2 hours from a mechanochemical treatment with chlorophyll. From the figure, Y, La,
The yield of Tb is independent of the presence or absence of glass shards,
0% or more. On the other hand, Ce is 60 to 70% when there are few glass fragments, which is lower than the case without glass fragments. However, when the glass shards are 30% or more, the yield tends to approach 90% without limit. Glass fragments should be inevitably mixed, regardless of the amount, when separating the fluorescent material from the waste fluorescent tube.Therefore, there was concern about the effect of the coexistence of the fluorescent material. It has been found that the mechanochemical treatment does not significantly affect the final acid leaching result of the rare metal component, but rather improves the leaching rate of the rare metal component when glass fragments are contained to some extent. Although not shown in the figure, Eu had the same tendency as Y, and showed a yield of about 5% lower. The reason is that BAT (Eu ²⁺ ) is difficult to dissolve.

In order to precipitate the rare metal component from a place where the rare metal component leached in, for example, hydrochloric acid as a weak acid is dissolved as a chloride, the pH is adjusted by controlling the pH of the solution. Can be separated in the precipitation stage by sequentially utilizing the selectivity in the reaction with other sulfate ions or nitrate ions, and can be separated and recovered in accordance with the intended use form. By firing, oxides of various rare metals can be obtained. If the content of the rare metal component is divided into two, the above separation operation becomes easy.

[0023]

According to the present invention, these can be separated into two types by type from waste fluorescent tubes containing rare metal components.
The final separation of each component is facilitated, enabling the recycling of scarce resources.

[Brief description of the drawings]

FIG. 1 shows XRD patterns of four types of monochromatic phosphors and their mechanochemically treated (upper and lower) for 120 minutes.

FIG. 2 shows a change in the yield of Y depending on the ball mill processing time when the rotation speed of the ball mill is changed.

FIG. 3 shows the relationship between the mechanochemical treatment time at a rotation speed of a ball mill of 400 rpm and the yield of an acid-extracted rare metal component.

FIG. 4 shows the relationship between the mechanochemical treatment time and the yield of acid-extracted rare metal components.

FIG. 5 shows the relationship between the change in the rotation speed of a ball mill in mechanochemicals and the yield of acid-extracted rare metal components depending on the treatment time.

FIG. 6 shows an XRD pattern after a mechanochemical treatment performed by changing the mixing ratio of glass fragments.

FIG. 7 shows the effect of the glass shard mixing ratio on the acid leaching yield of rare metal components.

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Claims (3)

[Claims] The waste fluorescent material containing a rare metal component is first subjected to a low-level mechanochemical treatment to elute the Y and Eu components into a weak acid, and then subjected to a high-level mechanochemical process to obtain La and Ce. A method of selectively separating a rare metal component from a waste fluorescent material, wherein the Tb component is eluted into a weak acid. 2. The method for selectively separating rare metal components from waste fluorescent material according to claim 1, wherein the degree of the mechanochemical treatment depends on the rotation speed and the treatment time of the ball mill. 3. The rotation speed and the processing time of the ball mill are 700 rpm and 2 hours at 400 rpm.
3. The method according to claim 2, wherein the rare metal component is selectively separated from the waste fluorescent material for 0 minutes.