KR101578389B1 - Method of recovering silver - Google Patents

Abstract

The present invention relates to a silver recovery method. According to the present invention, the silver recovery method comprises the steps of: oxidizing an alloy material (10) containing silver (Ag; 15) to produce nitrate (AgNO3); separating solid silver chloride (AgCl; 12) from the nitrate (b); recovering the silver chloride (12) as silver hydroxide (13) (c); and heating the silver hydroxide (13) to recover the silver (15).

Description

METHOD OF RECOVERING SILVER "

The present invention relates to a silver recovery method. More particularly, the present invention relates to a silver recovery method capable of recovering silver easily and safely by heating hydroxide generated in a wet refining process.

Precious metals such as silver, gold and the like have superior chemical stability than ordinary metals and do not change very well. They are used as high-grade accessories because of their rare value in their abundance, and they are used as catalysts from an industrial point of view.

Since the above precious metals are highly refined, they are not discarded even after they are used for the intended use, and it is necessary to reuse them through the process of recovering them in the form of pure noble metal again.

As an example of silver, silver recovery methods generally used include wet refining or electrolytic refining. In particular, wet refining is a method of selectively oxidizing or reducing a target noble metal in the form of liquid or solid phase using an acid, an alkali, an oxidizing agent, a reducing agent, etc., removing impurities through solid-liquid separation and recovering pure silver. It is a preferred method because it is more economical than refining.

However, chemical methods such as wet scouring can generate waste acid liquids and toxic gases. In a wet refining process that recovers silver, hydrazine (N ₂ H ₄ ) is used for silver reduction. Because hydrazine (N ₂ H ₄ ) is not only toxic in its own vapor but also ammonia (NH ₃ ) gas, which is generated by hydrazine (N ₂ H ₄ ) coming into contact with water (H ₂ O) There was a problem to be exposed. Further, in order to treat such toxic substances, there is a problem that an additional process is required and the process cost increases accordingly. Therefore, there is a need for a silver recovery method that can simplify the process while safely performing the silver reduction process.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method of recovering silver that is harmless to the human body and environmentally friendly.

It is another object of the present invention to provide a silver recovery method that simplifies the silver recovery process and reduces the process cost.

The above object of the present invention can be achieved by a method of manufacturing a semiconductor device, comprising: (a) preparing silver nitrate (AgNO ₃ ) by oxidizing an alloy material containing silver (Ag); (b) separating solid silver chloride (AgCl) from the nitrate; (c) reducing the silver chloride with silver hydroxide (AgOH); And (d) recovering the silver by heating the silver hydroxide.

In the step (a), the nitrate may be prepared by adding the alloy material to a nitric acid (HNO ₃ ) solution.

The step (b) may further include the steps of: (b1) adding sodium chloride (NaCl) to the nitrate to produce the chloride in the solid state; And (b2) solid-liquid separating the generated silver chloride.

(c1) reducing the silver chloride into the sodium hydroxide (NaOH) solution to form the solid hydroxide hydroxide; And (c2) subjecting the hydroxide hydroxide to solid-liquid separation.

In the step (d), the silver hydroxide may be heated to 200 ° C to 1300 ° C.

As the silver hydroxide is heated, the silver hydroxide may be reduced to silver oxide (AgO ₂ ) and the silver oxide may be reduced to silver (Ag) in that order.

The heating in the step (d) may be performed in an atmosphere of 0.001 mTorr to 1 Torr.

According to the present invention configured as described above, there is an effect that silver can be recovered by a method which is harmless to the human body and environmentally friendly.

Further, according to the present invention, there is an effect that the silver recovery process can be simplified and the process cost can be reduced.

1 is a chemical reaction formula showing a silver recovery process using wet refining.
2 is a diagram illustrating a silver recovery process according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating silver hydroxide (AgOH) according to one embodiment of the present invention.
4 is a view of a recovered silver bead according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views, and length and area, thickness, and the like may be exaggerated for convenience.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the present invention.

FIG. 1 is a chemical reaction formula showing a silver recovery process using wet refining, and FIG. 2 is a view illustrating a silver recovery process according to an embodiment of the present invention.

1 and 2, a silver recovery method according to an embodiment of the present invention includes the steps of (a) preparing silver nitrate (AgNO ₃ ) by oxidizing an alloy material 10 including silver (Ag) (c) separating silver chloride (AgCl; 12) from the nitrate salt; (c) reducing the silver chloride (AgCl) 12 with hydroxide silver (AgOH) To recover silver (Ag; 15).

The alloy material 10 containing silver may be composed of at least 90% of silver and the remaining 10% or less of copper (Cu), zinc (Zn), and the like. A general wet refining process for recovering silver from an alloy material 10 containing silver comprises the steps of (1) oxidizing the alloy material 10, (2) separating the solid silver chloride 12, (3) a step of reducing silver chloride (12) to silver (15).

First, the "(1) step of oxidizing the alloy material 10" is a step of adding the alloy material 10 containing silver to a nitric acid (HNO ₃ ) solution to form a solution containing nitrate such as AgNO ₃ , CuNO ₃ , ZnNO ₃ (See reaction formula (1) in FIG. 1, (1) and (2) in FIG. 2).

Next, the step (2) of separating solid silver chloride (12) is a step of adding sodium chloride (NaCl) to the solution containing the nitrate to produce solid silver chloride (12) (2) reaction scheme and FIG. 2 (3)] and solid-liquid separation of silver chloride (12) dispersed in a solid state in a sodium nitrate (NaNO ₃ ) solution. Solid-liquid separation is generally performed by separating solids dispersed in a solution, and filtrating the solids. The solid-liquid separation of the silver chloride (12) can be performed using a nanofilter, a microfilter, or the like so as to effectively separate solid silver chloride (12) particles.

Next, the step of (3) reducing silver chloride (12) to silver (15) is a step of reducing silver chloride (12) into sodium hydroxide (NaOH) (3) in FIG. 2, (4) and (5) in FIG. 2) and solid-liquid separation of the silver hydroxide 13 dispersed in a solid state in a sodium chloride (NaCl) solution. The solid-liquid separation of the silver hydroxide (13) can also be performed using a nanofilter, a microfilter, or the like.

On the other hand, a process of finally reducing the solid-liquid separated silver hydroxide (13) to silver (15) is further needed. Here, in the conventional wet refining process, pure silver 15 can be recovered by removing hydrazine (N ₂ H ₄ ), which is a reducing agent, into the hydroxide hydroxide 13 to remove OH ^- from the hydroxide hydroxide 13 (See reaction formula (4) in Fig. 1). However, the hydrazine is poisonous not only of the steam itself but also of the ammonia (NH ₃ ) gas (see the reaction formula (5) in FIG. 1) necessarily generated by hydrazine meeting with water (H ₂ O).

Therefore, the silver recovery method of the present invention is characterized in that silver hydroxide (13) is heated to recover silver (15) in the process of finally reducing hydroxide (13) to silver (15).

2 (6), the solid-liquid separated silver hydroxide 13 is introduced into the crucible 30 disposed in the chamber 20. Then, as shown in Fig. The mercury 13 can be heated (H) in a vacuum atmosphere in which the chamber 20 is closed and the inside of the chamber 20 is maintained at 0.001 mTorr to 1 Torr. The vacuum atmosphere inside the chamber 20 can be formed by injecting a reducing gas such as CO gas, H ₂ gas, or an inert gas such as Ar gas. In addition, a vacuum pump can be connected to the chamber 20 to create a vacuum atmosphere. The reason why the inside of the chamber 20 is formed in a vacuum atmosphere is because heating of the hydroxide hydroxide 13 in the atmosphere generates a large amount of silver oxide (AgO _x ), which can lower the recovery rate of silver (15).

The silver hydroxide 13 can be heated (H) to 200 ° C or higher, preferably 200 ° C to 1,300 ° C. The heating (H) time can be appropriately selected from 1 minute to 10 hours in consideration of the temperature rise time and the reduction time of the silver hydroxide (13).

From 200 ° C, silver hydroxide (13) can be reduced to silver oxide (Ag ₂ O) like 2AgOH -> Ag ₂ O + H ₂ O in a vacuum atmosphere. This is possible because OH ^- is relatively small in binding force with metals. Further heating (H), at a temperature of 280 ℃ the Eunsan cargo _{(Ag 2 O), Ag 2} O - , such as> 2Ag + 1 / 2O ₂ can be reduced to silver (Ag). In other words, as the silver hydroxide 13 is heated, the silver hydroxide 13 may be reduced to silver oxide and the silver oxide to silver. Here, when the silver hydroxide 13 is heated (H) at a melting temperature of 960 占 폚 or higher, which is further heated (H), and then subjected to a cooling process, silver beads are formed as shown in (7) Silver can be recovered.

(Example)

Hereinafter, the process of recovering the pure silver 15 from the alloy material 10 including silver through one embodiment will be described.

An alloy material 10 of 92.5% of silver (Ag) and 7.5% of copper (Cu) was used to recover the high purity (15) of 99.9% or more. First, the alloying material 10 was put into a nitric acid solution, and all alloys were made into liquid AgNO ₃ and CuNO ₃ nitrate. Subsequently, sodium chloride was added to the solution containing nitrate to selectively form only AgNO _{3 as} solid silver chloride (12). Subsequently, a mixture of silver chloride (12) and the liquid phase was solid-liquid separated to obtain a solid silver chloride (12) powder. Then, the silver chloride (12) powder was put into a sodium hydroxide solution to produce solid hydroxide silver (13). Then, as shown in Fig. 3, solid hydroxide hydroxide (13) powder was obtained by solid-liquid separation of the mixture of the hydroxide hydroxide (13) and the liquid phase.

The solid state hydroxide silver (13) powder was dried and placed in the alumina crucible (30), and the alumina crucible (30) was placed in the heat chamber (20). The pressure in the heat chamber 20 was maintained at 40 mTorr and the powder of mercury (13) was heated (H) at a temperature raising rate of 10 캜 / min from 200 캜 to 1050 캜 and heated (H) at 1050 캜 for 10 minutes To thereby melt the silver (15). Thereafter, the molten silver 15 was air-cooled, and silver (15) beads were recovered as shown in Fig.

As described above, the silver recovery method of the present invention is advantageous in that it is harmless to the human body and environmentally friendly because it can recover silver 15 by heating (H) the hydroxide silver 13 without using a toxic substance such as hydrazine . Further, since there is no need for an additional process for treating the toxic substance, the silver recovery process can be simplified and the process cost can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken in conjunction with the present invention. Variations and changes are possible. Such variations and modifications are to be considered as falling within the scope of the invention and the appended claims.

10: Alloy material containing silver
12: silver chloride (AgCl)
13: silver hydroxide (AgOH)
15: silver (Ag)
20: chamber
30: Crucible
H: heating

Claims (7)

(a) preparing silver nitrate (AgNO ₃ ) by oxidizing an alloy material containing silver (Ag);
(b) separating solid silver chloride (AgCl) from the nitrate;
(c) reducing the silver chloride with silver hydroxide (AgOH); And
(d) placing the hydroxide in the chamber and heating the silver hydroxide to 200 ° C to 1,300 ° C in a chamber atmosphere of 0.001 mTorr to 1 Torr to recover the silver
Wherein the silver recovery method comprises the steps of: The method according to claim 1,
Wherein the step (a) comprises adding the alloy material to a nitric acid (HNO ₃ ) solution to produce the nitrate salt. The method according to claim 1,
The step (b)
(b1) adding sodium chloride (NaCl) to the nitrate to produce the silver chloride in a solid state; And
(b2) separating the produced silver chloride by solid-liquid separation
Wherein the silver recovery method comprises the steps of: The method according to claim 1,
The step (c)
(c1) reducing the silver chloride into the sodium hydroxide (NaOH) solution to form the solid hydroxide hydroxide; And
(c2) separating the hydroxide hydroxide by solid-liquid separation
Wherein the silver recovery method comprises the steps of: delete The method according to claim 1,
Wherein the silver hydroxide is reduced to silver oxide (AgO ₂ ) and the silver oxide is reduced to silver (Ag) in the order of heating the silver hydroxide. delete

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