JP2003105570A - Precious metal recovery methods and recovery equipment - Google Patents

Abstract

(57) [Problem] To provide a method for recovering noble metal ions in noble metal ion-containing water in which iodine and the like coexist. SOLUTION: After selectively reducing iodine and the like, a noble metal ion is reduced and captured by using a carrier in which an anthrahydroquinone compound as a redox reaction reagent is carried on a porous carrier. Is done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention contains a high-concentration oxidizing substance such as an Au stripping solution in a gold (hereinafter also referred to as Au) plating step and an Au thin film etching solution generated in a semiconductor manufacturing step. The present invention relates to a method for recovering a precious metal from water containing a precious metal ion. In particular, it relates to a method for recovering Au from an aqueous solution containing Au ions.

[0002]

2. Description of the Related Art Precious metals, especially Au, are widely used in various fields such as electronic parts and plating materials, including ornaments.
It is an important precious metal indispensable to modern industry. For example, in semiconductor manufacturing, Au is thinned by a vapor deposition method or a plating method, and after a circuit is formed through a normal etching step, the next step is performed. In this process, a waste liquid such as an etching liquid using an iodine compound is generated.
The Au content in these waste liquids varies depending on the process in which they occur, but the etching liquid generally contains about 10 Au.
00 to 3000 mg / liter (hereinafter, also referred to as L), and the washing step liquid is several to 20 mg / L.

It is economically significant to recover Au from such a dilute aqueous solution containing Au ions, and it is a socially important task to reuse Au which is a limited resource. As a method of recovering this Au, for example, (1) a method of recovering by electrolysis, (2) a method of recovering by adsorbing it on an adsorbent such as activated carbon, (3) extracting from an aqueous solution with a chelating reagent dissolved in an organic solvent Methods etc. are considered.

However, each of these conventional recovery methods has the following drawbacks, and an efficient recovery method is required. That is, in the method (1), the concentration of Au in the solution decreases with the recovery, so that the recovery efficiency gradually decreases and the low concentration of Au ions cannot be recovered. In the method (2), a large amount coexists. Elemental and polyiodine ions (hereinafter,
Together, they are also called active iodine. ) Influences Au
However, the method (3), which has a low selectivity to Au and cannot efficiently separate Au, cannot be efficiently extracted because the selectivity to Au is low despite the use of an organic solvent having a high environmental load.

[0005]

On the other hand, as a method of selectively and efficiently recovering noble metal ions in an aqueous solution, a redox reaction reagent represented by a compound having a hydroquinone skeleton such as an anthrahydroquinone compound is adsorbed and immobilized on a porous carrier. The supported material (hereinafter, this supporting material is simply referred to as a metal ion treating agent) is packed in, for example, a column, and an aqueous solution containing a noble metal ion is passed through the solution so that the noble metal ion is converted into a zero-valent metal. A method of reducing and trapping with a metal ion treatment agent has been proposed (JP-A-7-185568).
This method has the advantages over the conventional ion exchange resins in that it has a better selectivity for noble metal ions and is easier to operate.

However, when the present inventor tried to recover Au by passing an Au etching aqueous solution containing active iodine through the column filled with the metal ion treating agent,
Even though the redox reaction reagent in the metal ion treatment agent is present in a reduced form (anthrahydroquinone form), the selectivity of the metal ion treatment agent for Au is lowered due to the effect of active iodine, and the recovery capacity is reduced. There was a drawback that it would be reduced. Therefore, the problem to be solved by the present invention is to use this metal ion treatment agent to selectively and efficiently extract only Au from a noble metal ion-containing water in which a large amount of active iodine coexists, particularly an Au ion-containing aqueous solution. It is to provide a method that can be collected well.

[0007]

In order to solve the above problems, in the present invention, a noble metal ion in water containing noble metal ions coexisting with active iodine (referred to as iodine and polyiodine ion. A noble metal characterized by selectively reducing active iodine in the recovery using a support (hereinafter referred to as a metal ion treating agent) in which an anthrahydroquinone compound as a redox reaction reagent is supported on a porous carrier. To provide a method of collecting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As the noble metal ion-containing water to be treated in the present invention, any noble metal ion-containing water in which active iodine coexists is adopted. For example, a gold stripping solution, a gold etching solution generated in a plating process or a semiconductor manufacturing process, or water discharged from these processes can be used. Hereinafter, these Au ion-containing waters will be described as an example.

In the present invention, the Au ions include monovalent Au ions represented by the chemical formula (1) below, or trivalent Au ions.

[0010]

[Chemical 1]

In the present invention, the active iodine has a higher redox potential than the anthrahydroquinone compound supported on the metal ion treating agent, lowers the selectivity for the Au ion to be recovered, and consequently the recovery capacity is increased. It is a substance having a lowering action, and specifically, it is an iodine or polyiodine ion represented by the following formula (2).

[0012]

[Chemical 2]

As a method for selectively reducing active iodine, specifically, active iodine is reduced using a reducing agent capable of selectively reducing only active iodine without reducing precious metal ions. Is the way. In the present invention, a reducing agent capable of selectively reducing only active iodine without reducing noble metal ions means a reducing agent which is inactivated by selectively reducing only active iodine, and is a noble metal ion such as Au ion. With respect to, a reducing agent that does not substantially exert a reducing action is meant. The drug suitable for the purpose of the present invention is at least one having a redox potential lower than that of active iodine represented by the following formula (3).

[Chemical 3]

However, even the reducing agents satisfying the above conditions are not suitable for the present invention.
That is, for example, hypophosphite, although having a redox potential lower than that of active iodine, was not found to have reactivity with active iodine. In addition, although stannous chloride has reactivity with active iodine, addition of tin salt requires wastewater treatment such as removal of precipitates, resulting in high environmental load. Furthermore, even if the active iodine in the aqueous solution is changed to an inactive state like hydrazines, A
A chemical that reduces u ions and immediately reduces them to metallic Au is not preferable because it involves complicated operations such as filtration of the fine Au precipitates that have been deposited.

From this point of view, preferable reducing agents for inactivating active iodine include hydroxylamines and thiosulfates. In the present invention, the active iodine can be reduced and inactivated by using thiosulfates or hydroxylamines alone, but the effect can be further enhanced by using both in combination. Hereinafter, the form of the inactivation treatment of active iodine in the present invention will be described in detail by using the effect of adding thiosulfate.

As the thiosulfate, any of sodium salt and potassium salt can be used. Among them, sodium thiosulfate pentahydrate represented by the following formula (4) is the most common and inexpensive, It is desirable in embodiments of the present invention.

[0017]

[Chemical 4]

Since the active iodine in the aqueous solution is selectively and quantitatively reduced by the reaction represented by the following formula (5) by the thiosulfate ion, it is possible to prevent the deterioration of the precious metal recovering ability of the metal ion treating agent. it can.

[0019]

[Chemical 5]

In the present invention, when the amount of thiosulfate added to the aqueous solution is less than the stoichiometric value of active iodine and the active iodine remains, the treating ability of the metal ion treating agent is only reduced. However, Au once reduced and deposited on the metal ion treatment agent is oxidized again and leaks into the treatment liquid, which is not preferable. The addition amount of the thiosulfate in the present invention is sufficient if it is at least the stoichiometric amount shown by the above formula (5), but it is preferably at least twice the molar amount of active iodine contained in the aqueous solution.

The thiosulfate added to the aqueous solution is treated as waste water after undergoing an Au recovery step using a metal ion treating agent. The thiosulfate ions and thionates represented by the formula (5) are It can be discharged outside the system as it is.

By using hydroxylamines instead of thiosulfate, the active iodine can be inactivated by the same principle and the metal can be recovered by using the metal ion treating agent. At this time, the inactivation treatment is presumed to be represented by the following formula (6), and since all the substances produced at this time become gas, they can be easily removed from the drainage system. The load on the environment due to the treatment is extremely small.

[0023]

[Chemical 6]

In the present invention, examples of the anthrahydroquinone compound include anthrahydroquinone (9,10
-Dihydroxyanthracene) and hydrogenated compounds thereof and their substitution products. Examples of the substituent in the substituent of the anthrahydroquinone compound include relatively hydrophobic substituents such as an alkyl group, an alkenyl group, an alkoxyl group, a phenyl group, an alkylamino group and a halogen group. The number of carbon atoms in the alkyl group, alkenyl group and alkoxyl group is 1 to 60, and practically 2
It is 4 or less, and the alkyl group may be linear or branched.

As long as the object of the present invention is not impaired, a substituent containing a sulfonic acid group, a sulfonic acid amide group or a carboxyl group can be adopted as a substituent of these anthrahydroquinone compounds. Since the metal ion treatment agent is used in an aqueous solution, a reducing compound having a hydrophobic substituent that generally does not elute in the aqueous solution is preferable.

The compounds having these substituents include
For example, 2-methylanthrahydroquinone, 2-ethylanthrahydroquinone, 2-amylanthrahydroquinone, 2-t-butylanthrahydroquinone, 2- (4-
Alkylated anthrahydroquinone compounds such as methylpentyl) anthrahydroquinone; Alkenylated anthrahydroquinone compounds such as 2- (4-methyl-pentenyl) anthrahydroquinone; Alkoxylation of 1-methoxyanthrahydroquinone, 1,5-dimethoxyanthrahydroquinone Anthrahydroquinone compounds; Phenyl-substituted anthrahydroquinone compounds such as 2-phenylanthrahydroquinone; Alkylaminated anthrahydroquinone compounds such as 2-N, N-dimethylaminoanthrahydroquinone; Halogen such as 1-chloroanthrahydroquinone and 2-chloroanthrahydroquinone Anthrahydroquinone compound.

Examples of hydrogenated compounds of hydroquinone compounds include 1,4-dihydro-9,10-dihydroxyanthracene and 1,2,3,4-tetrahydro-9,10-dihydroxyanthracene. These compounds may be used alone or in combination of two or more.

In the present invention, as the porous carrier, an inorganic porous carrier such as silicon dioxide, a carbon-based porous carrier such as activated carbon or activated carbon fiber, and other carbon particles such as activated carbon prepared to be hydrophobic, for example, , An aqueous emulsion processed product of polytetrafluoroethylene (JP-A-53-9298)
1), organic synthetic polymer particles, for example, a styrenedivinylbenzene copolymer used as an organic synthetic adsorbent or a molded product thereof, and activated carbon is particularly preferable because it is inexpensive and easily available.

[0029] To be suitably used for this porous carrier,
The standard pore size is 5 angstroms or more, preferably 10 angstroms or more, and the specific surface area is, for example, 1000 square meters per gram for a carbon-based porous carrier. These porous carriers may be in the form of powder, pellets, spheres or crushed products.

The smaller the particle size of the pelletized, spherical, or crushed product of this porous carrier, the better the contact efficiency, but when packed in a column or the like and continuously treated with an aqueous solution containing metal ions. Since the liquid resistance increases, for example, 0.3 to 2.5 mm is suitable for activated carbon.

In the present invention, as a method for preparing a metal ion treating agent in an aqueous solution by supporting an anthrahydroquinone compound as a redox reaction reagent on a porous carrier, an unstable compound such as an anthrahydroquinone compound is easily oxidized. In this case, a method of supporting using an oxide (anthraquinone compound) corresponding to the above redox reaction reagent can be adopted.

Examples of the oxide in this case include, as compounds corresponding to anthrahydroquinone, anthraquinone (9,10-anthraquinone), hydrogenated compounds thereof and anthraquinone compounds having the above-mentioned substituents.

In the present invention, the metal ion treating agent is generally prepared as follows. For example, as a batch-wise method, a solution of an oxide (anthraquinone compound) as a redox reaction reagent in a soluble organic solvent varies depending on the type of compound used and the solvent, but generally at room temperature or higher. Then, a porous carrier such as activated carbon is added, and while stirring, the oxide of the redox reaction reagent is impregnated into and adsorbed on this porous carrier, and the organic solvent is distilled off and dried to support the oxide. The product can be easily manufactured.

Further, if necessary, a solvent is added to the dried carrier to impregnate it, and then desalted water is added to the carrier to stir it while removing the oxide floating on the carrier without being adsorbed. After washing, the oxide support is kept as it is in a wet state. In addition, a solid porous carrier moistened with a solvent is packed in a column in advance, and a solution in which the oxide is dissolved is passed through the column,
It can also be carried out by carrying and washing. Furthermore, the metal ion treatment agent of the present invention can be prepared by subjecting the supported oxide to a reduction treatment.

As a method for reducing the supported material carrying the oxide, a method of reducing an ordinary anthraquinone compound to an anthrahydroquinone compound can be adopted.
For example, an aqueous solution of hydrosulfite such as sodium dithionite (sodium hydrosulfite) and potassium dithionite (potassium hydrosulfite) is preferably used, and depending on the type of other anthraquinone compound, sulfite or A zinc-acid (or alkali) -based reducing agent can be used. When the anthraquinone compound is reduced with sodium hydrosulfite, for example, an aqueous solution of sodium hydrosulfite in a stoichiometric amount or more is used in a batch manner or a supported material carrying the anthraquinone compound under conditions of pH 10 or less. It can be carried out by passing the solution through a column (column) or the like filled with and contacting it.

As the organic solvent used for the adsorption treatment,
Any redox reaction reagent can be used as long as it can dissolve the required amount of the oxide, but it is preferable to select a solvent that is soluble in the oxide and easily supported by the carrier to be used. As this organic solvent,
Generally, alcohols such as methanol, ethanol, propanol and isopropanol can be mentioned. Generally, the concentration of the solution of the oxide is preferably equal to or lower than its solubility and close to the saturated concentration.

The amount of the oxide supported is not particularly limited, depends on the type of solid porous carrier used, and is appropriately selected depending on the purpose of use and the like, but is generally 0.0
1-2 mol / liter-carrier, preferably 0.3-1.
0 mol / liter-carrier. If the supported amount is small, the cost will be higher than that of the recovered metal, and if the supported amount is too large, the amount that does not act on the metal ions will increase and the raw material will be wasted.

As a method for producing the metal ion treating agent of the present invention, a water-soluble salt of an anthrahydroquinone compound, which is a reducing compound of a redox reaction reagent, is used in addition to the method of supporting it on a carrier using the above-mentioned organic solvent. A method may be mentioned in which a porous carrier is added to the aqueous solution, the anthrahydroquinone compound is adsorbed on the porous carrier, the porous carrier is separated, and then washed.

As a method of recovering Au from an aqueous solution containing Au ions in the present invention, the thiosulfate ion is added to the aqueous solution in an amount equal to or more than the stoichiometric value of active iodine, and the mixture is stirred. A batch-type treatment method in which the supported material is separated by decantation or filtration can be adopted. Generally, the above-mentioned metal ion treatment agent is packed in a column (tower) and the aqueous solution is passed through. The method of processing is adopted. The method of passing the liquid through the column is not particularly limited, and a usual method can be used, and a method such as an upward flowing method or a downward flowing method can be appropriately adopted.

The metal ion treating agent is a method of reducing an anthraquinone compound as described above to an anthrahydroquinone compound when the metal ion treating agent has a loss of reducing ability when treating an aqueous solution containing Au, that is, a breakthrough. , For example, reduction with an aqueous solution of sodium hydrosulfite, or other nascent hydrogen (for example, zinc and hydrochloric acid or an alkaline aqueous solution) and the like, which have been subjected to reduction treatment by various reduction methods capable of reducing the anthraquinone compound of the present invention to an anthrahydroquinone compound. After that, the Au again
By treating the contained aqueous solution, the Au can be reduced and adsorbed and captured by repeating the treatment a considerable number of times, although there are some differences depending on the type of the redox reaction reagent supported.

A general method for reducing a metal ion treatment agent carrying a redox reaction reagent exhibiting a breakthrough oxidation type (quinone type) is to wash the breakthrough metal ion treatment agent with demineralized water or the like. After that, by performing the reduction treatment as described above, the Au-containing aqueous solution can be repeatedly treated with the metal ion treatment agent.

The metal ion treatment agent which has been repeatedly used and loses the ability to be finally regenerated and which has captured Au can be easily recovered as metal Au by incineration, for example. This incineration method is not particularly limited,
Any type of rotary incinerator such as a rotary kiln or a crucible type incinerator can be used as long as the metal Au is easily recovered from the incineration residue.
It is also possible to adopt a recovery method in which the captured Au is dissolved and recovered as Au ions by an oxidizing agent such as aqua regia.

After the treatment of the Au-containing aqueous solution with the metal ion treating agent in which the redox reaction reagent is carried on the porous carrier,
Au is reduced to a zero-valent metal on the treating agent, is selectively captured, and is hardly detected in the treated water. As a result of the powder X-ray diffraction analysis of the metal ion treatment agent that captured the Au-containing liquid, it was confirmed that Au was captured as metal Au.

The mechanism by which Au ions are trapped as metal Au on the metal ion treating agent has not yet been clearly analyzed, but it is estimated from the viewpoint of phenomena that when Au ions come into contact with the treating agent, the treating agent is treated. Is reduced by the anthrahydroquinone compound supported on the metal nuclei to form nuclei of metal Au, and electrons are exchanged through the nuclei to stack and grow the metal Au to form a metal Au coating film on the treating agent. I presume.

Further, during reduction and regeneration, electrons are transferred and received through the metal Au film laminated on the treating agent, and the supported quinone compound is reduced to a hydroquinone type compound, whereby It is presumed that Au ions are reduced and laminated on the treating agent.

In the present invention, it is possible to provide a noble metal recovery apparatus that adjusts the amount of the reducing agent added by utilizing the change in the characteristics of the aqueous solution due to the reduction of active iodine. In the present invention, with the progress of the reaction represented by the above formula (5), the dark brown Au etching solution or the like gradually increases in transparency,
When the reaction is complete, it becomes a colorless aqueous solution. By combining this change in color tone with a control device that has a photoelectric switch,
It is possible to design an Au recovery device that automatically senses the completion of the reaction and starts passing through the metal ion treatment agent.

Similarly, the initial redox potential is about 40.
It shows 0 mV (vs. silver-silver chloride electrode), but the oxidation-reduction potential gradually decreases with the progress of the reaction represented by the above formula (5), and becomes less than 250 mV at the end of the reaction. By using this change in redox potential and combining with a control device having a redox potential meter, the completion of the reaction is automatically sensed,
It is possible to design an Au recovery device that starts the passage of the metal ion treatment agent.

FIG. 1 shows an example of an automatic processing apparatus in which the indicated value of the redox potential meter and the pump are linked by utilizing the fact that the redox potential changes when the active iodine is inactivated. It is shown in the flow sheet. Au etching liquid storage tank 1
The aqueous thiosulfate or hydroxylamine salt solution in the aqueous thiosulfate or hydroxylamine salt solution storage tank 2 is supplied to the Au etching liquid stored in the tank 2 via the chemical injection pump 5. The redox potential of the Au etching solution is measured by the redox potential meter 3. The control device 4 controls the driving of the chemical injection pump 5 and the Au etching liquid treatment water delivery pump 6 based on the measurement value of the redox potential meter 3, and when the predetermined redox potential is reached, the control device 4 It operates so as to supply the activated Au etching liquid to the metal ion treatment agent-filled column 7.

[0049]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples,
Unless otherwise specified, "%" means "% by weight".

"Preparation of samples and the like" (a) "Preparation of a support (metal ion treatment agent) in which 1,4-dihydro-9,10-dihydroxyanthracene (hereinafter referred to as DDA) is supported on activated carbon" -108
According to 185, 1 liter of granular activated carbon (coal-based activated carbon manufactured by Mitsubishi Chemical Co., Ltd.) in which the air in the pores was replaced with nitrogen (487)
In g), 1950 g of an aqueous solution of a DDA disodium salt having a concentration of 16% (hereinafter, DDA disodium salt is referred to as "DDAN". The concentration of this DDA is expressed as a concentration converted to anthraquinone). In addition, it was adsorbed under reduced pressure for 2.5 hours. The mixture was suction filtered under a nitrogen atmosphere, the obtained filter cake was treated with 1 liter of a 10% sulfuric acid solution, and then washed with 1 liter of demineralized water substituted with nitrogen to obtain a metal ion treating agent.

(A) "Measurement of DDA supported amount of metal ion treating agent" 10 ml of the above metal ion treating agent was sampled and extracted with a mixed solvent of acetone / methanol (1: 1) using a Soxhlet extractor. After that, extraction with a toluene solvent was performed to extract DDA supported on activated carbon, and then these solvents were distilled off, and the weight of the remaining DDA was measured. As a result, the supported amount was 0.7 per 1 liter of activated carbon.
It was 3 mol.

(C) "Au etching liquid containing active iodine" The Au etching liquid used in the semiconductor manufacturing process was obtained. This Au etching solution has a dark brown color due to the action of active iodine, and the Au concentration is about 700 p.
It was pm.

(D) "Au etching water washing liquid containing active iodine" The Au etching water washing liquid discharged in the next step after obtaining the above (c) was obtained. The Au etching water washing liquid had a dark brown color due to the action of active iodine, and the Au concentration was about 20 ppm.

(E) "Preparation of aqueous thiosulfate ion solution" 500 g of sodium thiosulfate pentahydrate (Wako Pure Chemical Industries, Ltd.) was dissolved in 800 ml of pure water to make the total volume 1 liter.

(F) "Preparation of hydroxylamine aqueous solution" 50% hydroxylamine aqueous solution (Wako Pure Chemical Industries) 20
ml was collected and pure water was added to make the total volume 200 ml.

[Example 1] (1) 1 Beaker of Au etching solution described in "Inactivation treatment of Au etching solution containing active iodine" (C)
1 liter was collected. At this time, the Au etching solution exhibited a dark brown color due to the influence of active iodine, and the reading value of the redox potentiometer was 450 mV. While stirring
The described hydroxylamine aqueous solution was added slowly. As the hydroxylamine was added, the Au etchant gradually became transparent and eventually became a colorless aqueous solution.
At this time, the indicated value of the redox potentiometer was 98 mV. Then, by adding a small amount of the aqueous thiosulfate solution described in (e), Au did not precipitate and was stably present as Au ions.

(2) "Treatment of Au Etching Solution After Inactivation Treatment with Metal Ion Treatment Agent" (a) 10 ml of the metal ion treatment agent was collected in a wet state and filled in a glass column (Kiriyama Glass Co., Ltd.). did. The Au etching solution inactivated by the method described in (1) above was temporarily passed through a glass column filled with a metal ion treatment agent. The treatment liquid after passing through the column was appropriately sampled, the Au concentration was measured by ICP-atomic emission analysis, and the amount of Au trapped in the metal ion treatment agent after the passage treatment was determined. The results are summarized in Table 1. In the table, the flow rate is represented by the volume ratio to the filling amount of the metal ion treatment agent in the column (B
V) and the amount of Au captured were expressed as the amount captured per liter of the metal ion treatment agent (g / liter).

"Comparative Example 1" In the above-mentioned Example 1, the Au etching solution containing the active iodine described in (c) without the inactivation treatment of (1) was similarly treated with a metal ion treating agent. Processed. Collect the treated solution after passing through the column and
-The Au concentration was measured by atomic emission spectrometry, and the amount of Au captured by the metal ion treatment agent after the liquid passing treatment was determined. The results are summarized in Table 1 as in Example 1.

[0059]

[Table 1]

Example 2 (1) 1 liter of the Au etching water washing solution described in (D) "Inactivation treatment of Au etching water washing solution containing active iodine" was collected. The Au etching water washing solution turned brown due to the influence of active iodine, and the reading of the redox potentiometer was 440 mV.
Met. While stirring, the aqueous solution containing thiosulfate ion prepared in (e) was added, and when about 1.5 ml was added, A
The u etching water washing solution became a colorless aqueous solution. The indicated value of the redox potential at this time was 120 mV.

(2) "Treatment of Au Etching Water Washing Solution After Inactivation Treatment with Metal Ion Treatment Agent" In the same manner as in Example 1, the Au etching water washing solution inactivated by the method described in (1) above was treated. It processed using the metal ion processing agent. The aqueous solution after passing through the column was appropriately sampled, the Au concentration was measured by ICP-atomic emission analysis, and the amount of Au trapped in the metal ion treatment agent after the liquid passing treatment was determined. The results are shown in Example 1.
It is summarized in Table 2 in the same manner as.

Comparative Example 2 In the above-mentioned Example 2, the Au-etching washing solution containing the active iodine as described in (d) but without the inactivation treatment of (1) was similarly treated with a metal ion treating agent. Was treated with. Collect the aqueous solution after passing through the column,
The Au concentration was measured by ICP-atomic emission analysis, and the amount of Au captured by the metal ion treatment agent after the liquid passing treatment was determined.
The results are summarized in Table 2 as in Example 2.

[0063]

[Table 2]

[0064]

As described above in detail, the present invention has the following particularly advantageous effects, and its industrial utility value is extremely large. (1) By the method according to the present invention, Au can be recovered extremely easily from Au etching. We also succeeded in significantly reducing the Au recovery cost. Furthermore, since Au can be recovered from a dilute washing solution, even Au ions that have been conventionally discharged can be recovered, which greatly contributes to resource conservation. (2) According to the method of the present invention, it became possible to treat active iodine, which is originally a thick brown solution, in a colorless state. Moreover, the chemicals used have a very low environmental load. As a result, the costs associated with wastewater treatment have been significantly reduced.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of a processing apparatus used for carrying out the method of the present invention.

[Explanation of symbols]

1: Au etching solution storage tank 2: Thiosulfate or hydroxylamine salt aqueous solution storage tank 3: Redox potential meter 4: Controller 5: Chemical injection pump 6: Au etching solution treatment water delivery pump 7: Metal ion treatment agent Packed column

Claims (8)

[Claims] 1. A noble metal ion-containing water in which active iodine (referred to as iodine and polyiodine ion; the same applies hereinafter) coexists, and an anthrahydroquinone compound as a redox reaction reagent is supported on a porous carrier. A method for recovering a noble metal, which comprises selectively reducing active iodine in recovering using a supported material (hereinafter referred to as a metal ion treating agent). 2. A method for selectively reducing active iodine is
2. The method according to claim 1, which is a method of reducing active iodine by using a reducing agent capable of selectively reducing only active iodine without reducing noble metal ions. 3. The reducing agent capable of selectively reducing only active iodine without reducing noble metal ions is a compound selected from thiosulfates and hydroxylamines. the method of. 4. The noble metal ion is a gold ion.
4. The method according to any one of 3 to 3. 5. The method according to claim 4, wherein the aqueous solution containing gold ions is a gold stripping solution generated in a plating step or a semiconductor manufacturing step, a gold etching solution, or water discharged from these steps. . 6. The anthrahydroquinone compound is 9,1.
0-dihydroxyanthracene, 1,4-dihydro-
9,10-dihydroxyanthracene, 1,2,3,4
-The method according to any one of claims 1 to 5, which is at least one compound selected from tetrahydro-9,10-dihydroxyanthracene or a substitution product thereof. 7. The method according to claim 1, wherein the amount of the reducing agent added is adjusted by utilizing the change in the characteristics of the aqueous solution due to the reduction of active iodine. A precious metal recovery device for carrying out. 8. The precious metal recovery apparatus according to claim 7, wherein the change in the characteristics of the aqueous solution due to the reduction of active iodine is the color tone or the redox potential.