Method for recovering rare metal from optical glass waste

Abstract

To provide a method for inexpensively (economically) separating and recovering Ta and Nb from an optical glass waste by a relatively simple method.SOLUTION: A method of the present invention includes: (a) obtaining a first solution by dissolving an optical glass waste with mineral acid; (b) obtaining a glass melt residue containing Ta and Nb by filtering the first solution;(c) obtaining a second solution by dissolving the glass melt residue with sulfuric acid while adding hydrogen peroxide water; and (c) obtaining a third solution containing Ta and an insoluble residue containing Nb by filtering the second solution.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for recovering rare metals from optical glass waste materials, specifically, a method for recovering Ta and Nb from optical glass waste materials, and more specifically, a method for separating and recovering Ta and Nb from optical glass waste materials.

Background Art

[0002] Rare metal elements such as Ta, Nb, La, Gd, etc. (hereinafter referred to as "rare metals" in this specification) rely almost entirely on imports from overseas for their consumption. Therefore, it is difficult to ensure a stable supply, and they are also greatly affected by price fluctuations. On the other hand, rare metals are currently in a situation where they are discarded after being used in various applications. For example, although optical glass contains various rare metals including the above-mentioned rare metals, most of them are discarded in the manufacturing process, and the product is less than half of the raw materials. From such a situation, there is a need for a technology to efficiently and economically separate and recover rare metals from waste materials containing rare metals.

[0003] As a technology for recovering rare metals, Patent Document 1 discloses a method for separating and recovering rare metals from optical glass waste materials by the chlorination volatilization method. Further, Patent Document 2 discloses a method for recovering rare metal components from optical glass sludge generated from an optical glass polishing / washing process and an attached wastewater treatment device using sulfuric acid treatment or the like.

[0004] However, the method described in Patent Document 1 has complicated control of chlorine supply and heating temperature, and the method described in Patent Document 2 uses optical glass sludge as a raw material. Neither of them discloses a method for efficiently and economically, in other words, by a relatively simple method, recovering Ta and Nb with a high recovery rate from optical glass waste materials. Also, neither method of Patent Documents 1 and 2 discloses a method for separating and recovering Ta and Nb from optical glass waste materials.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to provide a method for recovering Ta and Nb from optical glass waste materials in a relatively simple and inexpensive (economical) manner, particularly a method for separating and recovering Ta and Nb.

Means for Solving the Problems

[0007] The present invention provides a method for recovering Ta and Nb from optical glass waste materials. The method includes: (a) dissolving the optical glass waste materials using a mineral acid to obtain a first dissolved solution; (b) filtering the first dissolved solution to obtain a glass dissolution residue containing Ta and Nb; (c) dissolving the glass dissolution residue with sulfuric acid while adding hydrogen peroxide solution to obtain a second dissolved solution; and (c) filtering the second dissolved solution to obtain a third dissolved solution containing Ta and an insoluble residue containing Nb.

[0008] In one aspect of the present invention, the step of obtaining the second dissolved solution in (c) includes dissolving the glass dissolution residue with sulfuric acid while adding hydrogen peroxide solution at a temperature of approximately 50°C to approximately 70°C.

[0009] In one aspect of the present invention, adding hydrogen peroxide solution in a range of approximately 20% to approximately 60% by volume ratio to sulfuric acid is included.

[0010] In one aspect of the present invention, the concentration of sulfuric acid is 3N to 9N, and adding hydrogen peroxide solution in a range of approximately 4% to approximately 60% by volume ratio is included.

[0011] In one aspect of the present invention, the mineral acid includes at least one of sulfuric acid, hydrochloric acid, or nitric acid.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the steps of the method according to an embodiment of the present invention.

[0014] In step S1 of FIG. 1, an optical glass waste material is prepared. The optical glass waste material is a glass waste material generated in the manufacturing process of optical glass and contains rare elements including rare metals. In one embodiment of the present invention, an optical glass waste material containing elements such as La, Gd, Zn, Zr, B, and Si in addition to Ta and Nb to be recovered is prepared. Note that the elements contained in addition to Ta and Nb are not limited to these elements, and the method of the present invention is applicable even when some of these elements or other elements are contained depending on the type of optical glass.

[0015] In step S2, the prepared optical glass waste material is dissolved using a mineral acid to obtain a first dissolved solution. The mineral acid is also called an inorganic acid and is an acid obtained by a chemical reaction of an inorganic compound. For example, hydrochloric acid (HCl), nitric acid (HNO 3 ), boric acid (H 3 BO 3 ), sulfuric acid (H 2 SO 4 ), carbonic acid (H 2 CO 3 ), phosphoric acid (H 3 PO 4) Hydrofluoric acid is applicable. In step S2, basically at least one or more of these mineral acids can be used. The concentration of the mineral acid is set to a predetermined concentration, and the temperature during dissolution can be, for example, approximately 50°C to approximately 70°C, but it is not limited to the temperature within this range.

[0016] The resulting solution obtained in step S2 does not contain any Ta and Nb, but contains other elements such as La, Gd, and B. The reason is that Ta 2 O 5 and Nb 2 O 5 correspond to so-called "poorly soluble substances", which are insoluble in water and not easily soluble in hydrochloric acid, nitric acid, dilute sulfuric acid, dilute perchloric acid, etc. Therefore, Ta 2 O 5 and Nb 2 O 5の It is necessary to dissolve the oxides of Ta and Nb. That is, although the method of using hydrofluoric acid to dissolve the oxides of Ta and Nb is common, when using hydrofluoric acid, it is extremely difficult to handle and there are many problems in industrialization. Therefore, the inventors of the present invention repeatedly conducted experiments while changing the types of mixed acids for the dissolution conditions of the glass dissolution residue that are more easily industrialized, and as a result, newly found the following steps (conditions).

[0017] In step S3, the obtained first solution is filtered to obtain a glass dissolution residue. In step S4, the obtained glass dissolution residue is dissolved with sulfuric acid while adding hydrogen peroxide solution to obtain a second solution. The concentration of sulfuric acid is set to a predetermined concentration, and the hydrogen peroxide solution may be added in a predetermined amount every predetermined time or continuously in a small amount under a predetermined temperature.

[0018] In step S5, the second leaching solution is filtered to obtain a third leaching solution containing Ta and an insoluble residue containing Nb. The reason why Ta and Nb can be separated into the leaching solution and the insoluble residue is that the inventors newly found that there are differences in their leaching conditions in step S4. Generally, a solvent extraction method that requires expensive large-scale equipment is usually applied for the separation of Ta and Nb. However, according to the present invention, it is possible to selectively obtain Ta that does not contain Nb in a relatively simple method and at low cost (economically).

[0019] The following are shown as examples with reference to the respective tables shown in FIGS. 2 to 4, indicating that Ta and Nb can actually be separated and recovered from the optical glass waste material by the method of one embodiment of the present invention shown in FIG. 1.

Examples

[0020] As the optical glass waste material, an optical glass waste material containing elements such as La, Gd, and B in addition to Ta and Nb was prepared. The results of dissolving the optical glass waste material using three mineral acids, sulfuric acid, hydrochloric acid, and nitric acid, are shown in FIG. 2. The concentrations of the respective acids differed from 3N to 7N, and the dissolution temperatures also differed between 50°C and 70°C. However, it was confirmed that neither Nb nor Ta was present (eluted) in the leaching solution under any of the conditions of No. 1 to No. 6. That is, it was found that Nb and Ta were concentrated in the glass leaching residue obtained by filtering the leaching solution.

[0021] Next, first, the optical glass waste material was dissolved at a temperature of 70°C using hydrochloric acid with a concentration of 6N corresponding to the condition of N.4 in FIG. 1. After the leaching solution was filtered, washed with water, the residue was naturally dried and pulverized in a mortar to prepare a glass leaching residue mainly containing Ta and Nb. As the conditions during the dissolution test of this glass leaching residue, sulfuric acid and hydrochloric acid were used as the acids, hydrogen peroxide water was added, and the mixture was stirred for a certain period of time. The solution concentration after filtration was analyzed by ICP.

[0022] From the analysis results by ICP, since elution of Ta and Nb was confirmed under the conditions using sulfuric acid and hydrogen peroxide solution, tests were conducted while changing the conditions with this combination. In the tests, the temperature was changed to room temperature (RT), 50 °C, and 70 °C. The reference condition was to dissolve 3.0 g of glass dissolution residue in 50 ml of sulfuric acid. In the tests, hydrogen peroxide was added in 10 ml increments up to 30 ml every hour starting from the dissolution test with sulfuric acid only. These test results are shown in Figure 3.

[0023] From Figure 3, at each temperature, by adding hydrogen peroxide solution (H 2 SO 4 ) to sulfuric acid (H 2 O 2 ), it was found that the elution of Ta can be increased to 2 - 11 (g / L), about 10 to 100 times that of Ta, while suppressing the elution of Nb to a range of 0 - 0.6 (g / L) close to zero. For example, when adding 20 ml of hydrogen peroxide solution after 3 hours at a temperature of 50 °C, the elution of Nb could be suppressed to 0.1 (g / L) or less while increasing the elution of Ta to 5.4 (g / L). Furthermore, at a temperature of 70 °C, by adding 10 ml of hydrogen peroxide solution after 2 hours, the elution of Ta could be made 4 (g / L) while suppressing the elution of Nb to zero, and by adding 20 ml of hydrogen peroxide solution after 3 hours, the elution of Ta could be made 5.1 (g / L) while suppressing the elution of Nb to zero.

[0024] Next, the test results in Figure 3 were compared with the theoretical concentration of the glass residue (the metal concentration in the dissolution solution obtained when all was dissolved), and the results of obtaining the elution rates (%) of Ta and Nb are shown in Figure 4. From Figure 4, it was found that the dissolution behaviors of Ta and Nb differ depending on the conditions. That is, at room temperature, it is possible to increase the elution rate of Ta to 100% by adding hydrogen peroxide solution, but at the same time, the elution rate of Nb is also about several tens of percent and shows a relatively high tendency.

[0025] However, it has been revealed that when the temperature is 50°C or higher, by increasing the amount of hydrogen peroxide added, the elution rate of Nb can be significantly suppressed with respect to the elution rate of Ta. For example, it has been found that when adding 30 ml of hydrogen peroxide solution after 4 hours at a temperature of 50°C, the elution rate of Ta can be increased to 56% - 72% while suppressing the elution rate of Nb to 0%. Also, for example, it has been found that when adding 20 ml of hydrogen peroxide solution after 3 hours at a temperature of 70°C, the elution rate of Ta can be increased to 22% - 57% while suppressing the elution rate of Nb to 0%.

[0026] In the experiment conducted by the inventors to obtain specific conditions to support the results of FIG. 4, glass dissolution residue was added to 50 mL of sulfuric acid, and hydrogen peroxide solution was added to the sulfuric acid solution at a volume ratio of 20% - 60% while controlling the temperature at room temperature, 50°C, and 70°C. As a result, it was found that a Ta eluate containing no Nb can be obtained when dissolving at a sulfuric acid concentration of 3N - 9N, a temperature of 50°C - 70°C, and an addition amount of hydrogen peroxide solution of about 40% - 60%. That is, it has been found that Ta and Nb can be separated and recovered from the optical glass waste material under the above-described conditions.

[0027] The embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments. The present invention can be implemented in various modified, corrected, and deformed forms based on the knowledge of those skilled in the art without departing from its gist.

Claims

Claim 1 A method for recovering Ta and Nb from waste optical glass, comprising: dissolving the waste optical glass using a mineral acid to obtain a first dissolved solution; filtering the first dissolved solution to obtain a glass dissolution residue containing Ta and Nb; dissolving the glass dissolution residue with sulfuric acid while adding hydrogen peroxide solution to obtain a second dissolved solution; filtering the second dissolved solution to obtain a third dissolved solution containing Ta and an insoluble residue containing Nb. Claim 2 The method according to claim 1, wherein the step of obtaining the second dissolved solution comprises dissolving the glass dissolution residue with sulfuric acid while adding hydrogen peroxide solution at a temperature of approximately 50°C to approximately 70°C. Claim 3 The method according to claim 2, comprising adding hydrogen peroxide solution in a volume ratio range of approximately 20% to approximately 60% with respect to sulfuric acid. Claim 4 The method according to claim 2 or 3, wherein the concentration of sulfuric acid is 3N to 9N, and hydrogen peroxide solution is added in a volume ratio range of approximately 40% to approximately 60%. Claim 5 The method according to claim 4, wherein the mineral acid comprises at least one of sulfuric acid, hydrochloric acid, and nitric acid.

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