KR101301526B1 - Manufacturing method of potassium silver cyanide solution using air bubbling - Google Patents

Abstract

Disclosed is a method for preparing a Potassium Silver Cyanide (KAg (CN) ₂ ; PSC) solution using Air Bubbling.
Method for producing a PSC solution according to the present invention comprises the steps of: (a) immersing a cathode electrode and a cathode electrode of silver (Ag) material in a cell in which potassium cyanide solution is stored; And (b) applying a voltage to the cathode and anode electrodes of the cell to leach silver into the potassium cyanide solution. In step (b), the air is applied to the cell to which the voltage is applied. It is characterized by performing bubbling.

Description

MANUFACTURING METHOD OF POTASSIUM SILVER CYANIDE SOLUTION USING AIR BUBBLING}

The present invention relates to a technique for preparing potassium cyanide (Potassium Silver Cyanide, KAg (CN) ₂ ; hereinafter referred to as 'PSC') solution, and more particularly, to a method for preparing PSC solution using air bubbling.

Today, electric circuit devices and semiconductor devices continue to be miniaturized and highly integrated. In order to design precise circuit lines, it is essential to select metal materials with low resistivity and precision processing.

The most commonly used raw materials that meet these properties are known as gold (Au) and silver (Ag). In order to apply gold and silver to a circuit board, rather than directly using the malleability, a method of manufacturing a precision circuit by applying it to a circuit using a complex compound prepared by oxidizing gold and silver and reducing it by electroplating is common. It is.

As a complex compound of gold and silver, materials most widely used for semiconductor electrode lines, printed circuit board (PCB) electrode lines, plating, and the like are PGC (Potassium Gold Cyanide) or PSC (Potassium Silver Cyanide). PGC and PSC have good secondary processability and excellent electrodeposition property, so they are useful for products of complex shape after press processing.

In general, the main method for synthesizing cyanide compounds of gold and silver is chemical synthesis. Chemical synthesis consists of three steps: leaching, synthesis and crystallization. In this chemical synthesis, first, gold and silver are reacted with nitric acid to dissolve, and then precipitated with NaCN to form AuCN and AgCN crystals, which are dissolved in KCN solution and then synthesized with cyanide powder through crystallization.

However, this method has disadvantages such as toxicity of cyan toxin, consumption of large amount of reactants, and large amount of toxic wastewater discharged. Recently, research has been conducted to proceed silver plating using electroless plating without the use of highly toxic cyanide, but it is still difficult to commercialize due to the larger crystal grains and poor adhesion compared to cyan plating.

Related prior art documents include a method for producing potassium cyanide by the electrolytic oxidation method disclosed in Republic of Korea Patent Publication No. 10-1990-0018419 (published on December 21, 1990).

It is an object of the present invention to provide a method for preparing a PSC solution which can increase the leaching rate of silver in potassium cyanide solution as compared to chemical leaching.

PSC solution production method according to the present invention for achieving the above object, (a) immersing a cathode electrode (Cathode Electrode) and an anode electrode (Ag) material in a cell in which a potassium cyanide (KCN) solution is stored; And (b) applying a voltage to the cathode and anode electrodes of the cell, thereby leaching silver (Ag) into a potassium cyanide (KCN) solution; and in the step (b), the voltage Air bubbling is performed on the applied cell.

In the PSC solution preparation method according to the present invention, by leaching the potassium cyanide solution in the leaching process of silver to which the electrochemical electroleaching method is applied, the dissolution rate of silver in the potassium cyanide solution can be increased by increasing the dissolution rate of silver.

1 is a flowchart illustrating a PSC solution preparation method according to an embodiment of the present invention.
2 is a view schematically showing a PSC solution preparation apparatus according to the present invention.
Figure 3 is a graph showing the mass change amount of the silver electrode according to the leaching reaction time of Examples 1, 2 and Comparative Examples according to the present invention.
Figure 4 is a graph showing the amount of change in the current according to the leaching reaction time of Examples 1, 2 and Comparative Examples according to the present invention.
5 is a graph showing the dissolved oxygen amount according to leaching reaction time of Examples 1, 2 and Comparative Examples according to the present invention.
6 is a view schematically showing the surface change of the silver electrode according to the leaching reaction time of the comparative example of the present invention.
7 to 9 are scanning electron microscope (SEM) photographs of the front, rear, and cross-sections of the counter electrode in a state in which the silver electrode of the leaching reaction process of the comparative example of the present invention is washed with distilled water and then dried.

Potassium cyanide (Potassium Silver Cyanide, KAg (CN) ₂ ; hereinafter referred to as 'PSC') solution preparation method according to the present invention, (a) immersing a cathode electrode (Cathode Electrode) and an anode electrode (Ag) material in a cell in which a potassium cyanide (hereinafter referred to as 'KCN') solution is stored; And (b) applying a voltage to the cathode and anode electrodes of the cell, thereby leaching silver (Ag) into the KCN solution; and in step (b), the cell to which the voltage is applied It characterized in that the air bubbling (Air Bubbling).

Air bubbling of the step (b) is characterized in that carried out for 30 minutes to 2 hours.

In the step (b), it characterized in that the stirring (Stirring) the KCN solution.

In the step (a), it is characterized in that further forming a cation exchange membrane (Proton Exchange membrane; PEM) between the cathode electrode and the anode electrode.

The cathode electrode is characterized by using an insoluble metal material for the KCN solution.

The cathode electrode is characterized in that the stainless steel (SUS) material.

Hereinafter, a PSC solution preparation method according to the present invention will be described with reference to the accompanying drawings.

1 is a flowchart illustrating a PSC solution manufacturing method according to an embodiment of the present invention, Figure 2 is a schematic view showing a PSC solution manufacturing apparatus according to the present invention.

Referring to FIG. 1, the PSC solution preparation method according to an embodiment of the present invention includes an electrode immersion step (S10) and a silver leaching step (Sg) using air bubbling (Air Bubbling) in a KCN solution. do.

1 and 2, in the electrode immersion step (S10) in the KCN solution KCN solution (110) The positive electrode 130 and the negative electrode 140 made of silver (Ag) may be immersed in the stored cell 120.

In the PSC solution manufacturing apparatus, the cell 120 is an electrolytic cell having an accommodation space to store the KCN solution 110. For example, the cell 120 may be made of acryl.

Anode Electrode (130) To manufacture For the leaching function of silver (Ag) for preparing the PSC solution may be formed of a silver (Ag) material, it may be provided on a plate (Plate).

The cathode electrode 140 is a counter electrode of the anode electrode 130, and may use an insoluble metal material for the KCN solution 110. For example, the cathode electrode 140 may be made of stainless steel (hereinafter, referred to as 'SUS'), and may be provided in a plate shape.

Meanwhile, a proton exchange membrane (PEM) 150 may be further formed between the positive electrode 130 and the negative electrode 140 to separate the positive electrode 130 and the negative electrode 140 from each other. It is easy to control the cation movement from the anode electrode 130 to the cathode electrode 140 through the cation exchange membrane 150, the silver cyanide synthesis is advantageous.

As the cation exchange membrane 150, for example, a fluorine-based polymer electrolyte membrane represented by Nafion having excellent ion conductivity may be used. For example, the cation exchange membrane 150 may use Nafion 117 (manufactured by Dupont).

When the cation exchange membrane 150 is formed, the anode electrode 130 and the cathode electrode 140 are separated from each other by the cation exchange membrane 150 such that one cell 120 includes an anode chamber including the anode electrode 130 ( It may be separated into a cathode chamber (not shown) including a cathode electrode 140 and not shown.

The KCN solution 110 is an electrolyte, which is 2 wt% to 10 wt% of KCN dissolved in water (H ₂ O) so that leaching (elution or elution) of silver (Ag) in the PSC solution to be produced may occur actively. 1 L of KCN solution by weight.

If the KCN solution 110 is less than 2% by weight, it is not possible to sufficiently secure the leaching amount of silver (Ag) in the PSC solution to be prepared. On the other hand, when the KCN solution 110 is more than 10% by weight, since the K ⁺ ions remaining without being involved in leaching of silver (Ag) is increased, the material cost may increase.

In the silver leaching step (S20) of FIG. 1, a constant voltage 160 is applied to each of the positive electrode 130 and the negative electrode 140 immersed in the KCN solution 110 stored in the cell 120, and then reactive. Ag is leached into the KCN solution 110 while air bubbling is performed to increase.

After a wire (not shown) is connected to each of the anode electrode 130 and the cathode electrode 140, a constant voltage 160 is applied, and air bubbling causes silver (Ag) to leach into the KCN solution 110. do. The theoretical background on PSC synthesis will be explained through [Equation 1] to [Equation 8] shown below.

When silver (Ag) reacts with cyanide (CN), Ag must have a monovalent oxidation number through electron exchange [Equation 1], and at a bonding ratio of 1: 2, that is, Ag (CN) ₂ ^- is the most stable compound. It is known to form [Formula 2]. The process of leaching Ag into CN requires electron transfer, and it is common to involve the reaction of the two steps of the following [Formula 1] and [Formula 2].

^{Ag + CN - → AgCN + e} - ---- [ Equation 1]

^{AgCN + CN - → Ag (CN} ) 2 - ---- [ Formula 2]

Analyzing this process in more detail, Habashi and Hiskey and others mentioned the necessity of oxygen in the silver leaching process. In one step, Ag was leached into potassium cyanide solution. Emission is the same as the reaction mechanism of [Equation 1] described above, but there is a difference in the process of oxygen absorption electrons.

In high-purity Ag, four electrons by Griffith model are adsorbed and reacted at the same time as shown in [Equation 3], but when bismuth (Bi) or lead (Pb) is mixed with impurities, fouling model as shown in [Equation 4] According to the Pauling model, two electrons were first adsorbed, and then a multistage reaction was carried out to adsorb two electrons again.

^{Ag + CN - → AgCN + e} - ---- [ Equation 1]

O _{2 ^{+ H 2 O + 4e - →}} 4 OH - ---- [ Equation 3]

O _{2 ^{+ H 2 O + 2 e -}} → HO 2 - + OH -, HO 2 - + H 2 O + 2 e - → 3 OH - ---- [ Expression 4]

Ag + 2 KCN + 1/4 O ₂ + 1/2 H ₂ O → KAg (CN) ₂ + KOH ---- [Equation 5]

In the course of the above reaction it can be seen that PSC is synthesized at the positive electrode and OH ⁻ is formed at the negative electrode [Equation 5].

In this case, since one equivalent of PSC is made from two equivalents of KCN, one equivalent of K ⁺ ions does not participate in the reaction and remains in the positive electrolyte solution. The ions remaining in the positive electrolyte solution are transferred to the negative electrode through the cation exchange membrane to be electrically neutralized with the OH ⁻ ions, and the pH of the negative electrode may be expected to increase.

In other words, it can be seen that the effect of controlling the equivalence ratio of the reaction system is possible by removing K ⁺ from the positive electrolyte using a cation exchange membrane and selectively permeating the negative electrode.

Looking at the minimum voltage for the electrolytic leaching of Ag, the standard reduction voltage of _Ag E ⁰ _{[ Ag ]} = 0.799 V (see [Equation 6]), the standard reduction voltage of oxygen E ⁰ _[O] = 0.23 V, hydrogen standard reduction voltage E ⁰ _[H] = 0V. When the resistance value of the solution is calculated as 50% of the total voltage, it can be seen that the minimum voltage for Ag electroleaching is 1.529V (see [Equation 7] and [Equation 8]).

Here, the electrochemical equivalent represents the mass of the element precipitated on the electrode when the current of 1A flows for 1 second, the theoretical leaching amount of Ag is 1.1180 mg / C, 4.0248 g / hr.

^{Ag = Ag + + e -,} E 0 [Ag] = 0.799V ---- [ Equation 6]

E ⁰ _{[ Ag ]} + E ⁰ _[O] + E ⁰ _[H] + R (resistance of solution) = 1.529 V ---- [Equation 7]

0.799V + 0.23V + 0V + 0.5V (50% of the total voltage) = 1.529V ---- [Equation 8]

In the present invention, air is bubbled during the electrolytic leaching process of silver to supply air to the KCN solution 110. In this case, since the oxygen necessary for dissolving silver can be sufficiently supplied, the leaching rate of silver in the KCN solution 110 may be increased. It becomes possible.

At this time, the air bubbling is preferably performed for at least 30 minutes or more, preferably 30 minutes to 2 hours to supply sufficient oxygen to the KCN solution 110 to achieve the dissolution rate of silver 100%.

When the air bubbling is performed for less than 30 minutes, the dissolution rate of silver in the KCN solution 110 may not be 100%, and thus the leaching rate of silver may decrease. On the other hand, if air bubbling is performed for more than 2 hours, the effect of increasing the dissolution rate of silver can no longer be expected, and productivity may be lowered.

In addition, according to the present invention, the KCN solution 110 may be further stirred while performing air bubbling to increase the current intensity to increase the cyanation reaction rate. In this case, the leaching rate of silver in the KCN solution 110 may be increased.

Hereinafter, a method for producing a PSC solution according to the present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

Example  One

Under a temperature of 25 ° C. and a pressure of 1 atm, an acryl cell having a size of 135 mm × 100 mm × 90 mm was prepared. The cell is separated by a cation exchange membrane and is composed of a cathode chamber and an anode chamber. At this time, a silver plate of 50 mm × 150 mm size was used as the anode electrode, and a stainless steel plate of 50 mm × 150 mm size was used as the cathode electrode. The positive electrode and the negative electrode were spaced 2.5 cm apart.

A cation exchange membrane was installed between Nafion 117 having a size of 8.0 cm × 8.0 cm between the anode electrode and the cathode electrode to facilitate cation transport control. As a solution, 1 L of 4 wt% KCN solution (manufactured by Junsei) in which KCN was dissolved in water (H ₂ O) was used.

After connecting the wires to the electrodes of each chamber, a constant voltage of 2.5V was applied, and air bubbled to react.

Example  2

When carrying out air bubbling, the Ag electroleaching process was performed in the same manner as in Example 1 except that the KCN solution was further stirred.

Comparative example

Except not performing air bubbling, the Ag electrolytic leaching process was performed in the same manner as in Example 1.

Character rating

<Amount of Mass and Current of Ag Electrode>

In Examples 1, 2, and Comparative Example, while the leaching reaction was performed for a certain time, the change of the mass and current of the Ag electrode according to the reaction time was measured, and the results are shown in FIGS. 3 and 4, respectively. In addition, the electrochemical equivalents in Examples 1, 2 and a comparative example were calculated and shown in Table 1.

At this time, the mass change amount of the Ag electrode was investigated by using an Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) Optima 7300DV (manufactured by PerkinElmer) after collecting the leachate during the leaching reaction. It was measured by. The current variation of the Ag electrode was measured using Vupower K3010 (manufactured by Aiken).

Hydrogen ion concentration and dissolved oxygen content

While conducting a leaching reaction for a predetermined time for Examples 1, 2 and Comparative Example, the hydrogen ion concentration of the reaction time was measured using Orion 3 star (manufactured by Theromoscientific) in KCN solution of each electrode, and Model 58 (Yellow Springs Instruments Co., Inc., manufactured) to measure the amount of dissolved oxygen according to the reaction time, and the results are shown in Table 2 and FIG. 5, respectively.

<Ag ion concentration>

The concentration of silver (Ag) ions in the positive electrode and negative electrode electrolyte solutions of Example 1 and Comparative Example was measured, and the results are shown in Table 3.

<Ag electrode analysis in the reaction process>

The surface change of the silver electrode was observed while the leaching reaction was conducted for a predetermined time for the comparative example, and the silver electrode of the leaching reaction process was washed with distilled water and then dried in front of the counter electrode, and the cross section. Were analyzed using a scanning electron microscope (SEM) and an energy dispersive spectroscopy (EDS), and the results are shown in FIGS. 7 to 9 and Table 4, respectively.

3 is a graph showing the mass change of the silver electrode according to the leaching reaction time of Examples 1, 2 and Comparative Example according to the present invention, Figure 4 is a leaching reaction time of Examples 1, 2 and Comparative Example according to the present invention It is a graph showing the amount of change in current.

Referring to FIG. 3, compared to Example 2 and Comparative Example, it was confirmed that Example 1 has the fastest dissolving rate of silver electrodes in KCN solution. In Example 1, when 20 minutes passed, 80.9% of the silver electrode was dissolved relative to the initial mass, and all silver electrodes contained in the KCN solution were dissolved before 30 minutes passed. In particular, in Example 1, it was confirmed that the silver electrode was dissolved at a rate about four times faster than the comparative example.

However, Example 1 which carried out air bubbling and Example 2 which carried out air bubbling and stirring at the same time showed little difference.

As described above, it can be seen that oxygen in the air is involved in the reaction because the dissolution rate of the silver electrode dissolved in the KCN solution is faster than that of the comparative examples.

However, when the stirring and air bubbling were performed at the same time, the dissolution rate of the silver electrode was expected to be the highest. It was observed that the oxygen supply to the surface was rather smooth.

Referring to FIG. 4, Examples 1 and 2 observed that an electric current flowed about 4 to 4.8 times stronger than the comparative example. In particular, Example 1 had the best current flow compared to Example 2 and Comparative Example, and the current flow was about four times better than Comparative Example.

In Example 2, the current flowed about 1.3 times worse than that in Example 1, but the current flowed about 3 times as compared with the comparative example. This can be seen that the bubbling or stirring of the potassium cyanide solution, which is an electrolyte solution, activates the flow of ions in the potassium cyanide solution to improve the current flow.

On the other hand, in Examples 1, 2 and Comparative Examples, the current tended to decrease slightly over time, which can be seen as the current decreases as the silver electrode dissolves and the reaction surface area decreases over time.

Through the measurement results of the mass change amount and the current change amount of the silver electrode according to the leaching reaction time, it was confirmed that the change of mass and the intensity of the current according to Examples 1, 2 and Comparative Examples are the same. It was found that the silver electrode was closely related to the melting of the silver electrode.

That is, the current may be used as an indicator of the solubility of the silver electrode, and it was confirmed that the bubbling air or stirring the solution was very advantageous for the cyanation reaction of the silver electrode.

Table 1 below shows the calculated electrochemical equivalents in Examples 1, 2 and Comparative Examples of the present invention.

[Table 1]

Referring to Table 1, Example 1 subjected to air bubbling and Comparative Example without any condition showed higher electrochemical equivalents than Example 2 subjected to air bubbling and stirring.

Although the comparative example showed the best efficiency, the reaction rate is slow, and thus, the method of practically utilizing silver cyanide in synthesis may be most suitable for Example 1 in which air bubbling was performed.

On the other hand, the electrochemical equivalent of more than 100% can be considered to be due to the chemical solubility action by KCN solution as well as the electrolytic dissolution in cyanide leaching of silver.

5 is a graph showing the dissolved oxygen amount according to leaching reaction time of Examples 1, 2 and Comparative Examples according to the present invention.

Referring to FIG. 5, in the case of Examples 1 and 2, the dissolved oxygen amount was kept constant in the state of about 2 to 3.5 ppm increase compared to Comparative Example 1, and it was found that the dissolved oxygen reduction ratio was small. This is consistent with the need for oxygen to dissolve silver, as Hiskey and Habasi mentioned.

Table 2 below shows the hydrogen ion concentration (pH) value in the KCN solution of each electrode according to leaching reaction time in Examples 1, 2 and Comparative Examples of the present invention.

[Table 2]

Referring to Table 2, in Examples 1, 2 and Comparative Examples, the positive electrode (+) showed little change in pH, the negative electrode (-) showed a tendency to increase by about 0.7 ~ 4.9% compared to the initial. This negative electrode due to water electrolysis reactions is formed with a hydrogen gas in the positive (+) and negative () (-) it is the pH gradient was formed between the positive electrode non-reactive in the (+) K ⁺ ions are cation exchange It can be seen that the pH was increased while passing through the membrane to the cathode (-) to achieve electrical neutrality with OH ^- ions.

In particular, it can be seen that Examples 1 and 2 have a larger pH change of the negative electrode (-) than the comparative example. Through this, it can be seen that the change in mass and the pH change of the silver electrode.

Table 3 below shows the measured concentration of silver (Ag) ions in the KCN solution of the positive electrode and the negative electrode in Example 1 and Comparative Example of the present invention.

[Table 3]

Referring to Table 3, in Example 1 and Comparative Example, the amount of silver ions increased with time at the positive electrode, but silver ions were not detected at the negative electrode. This may be because silver reacts with cyan ions at a very high rate when electrolytically dissolved in KCN solution to form a complex compound of anion such as neutral or Ag (CN) ₂ ⁻ .

If some cations are formed during electrolysis, silver ions may be detected at the cathode because the cations move through the cation exchange membrane to the cathode, but the anion was not detected at the cathode. .

6 is a view schematically showing the surface change of the silver electrode according to the leaching reaction time of the comparative example of the present invention.

Referring to FIG. 6, as a result of looking at the surface of the silver electrode 610 which is the anode electrode by applying a voltage in a comparative example in the absence of solution agitation or air bubbling, when 10 minutes have passed after the reaction, the silver in the KCN solution It was observed that a white film 620 was formed on the surface of the electrode 610 (a). When 60 minutes had elapsed, it was observed that the uppermost portion (A) of the silver electrode 610 in the KCN solution rapidly dissolved (b). Then, when more than 60 minutes, the etching phenomenon (B) was observed in the uppermost part of the silver electrode 610 in the KCN solution (see A in Fig. 6 (b)) (c). This is because the white film 620 formed on the surface of the silver electrode 610 acts as a resistance, so that a large current flows in a portion close to the power supply in the KCN solution, and thus, leaching occurs actively in this portion.

7 to 9 are sequentially scanning electron microscope (SEM) photographs of the front, rear, and cross-sections of the counter electrode in a state in which the silver electrode of the leaching reaction process of the comparative example of the present invention was washed with distilled water and dried. Table 4 shows the results of EDS analysis of the silver electrode during the leaching reaction.

Referring to FIGS. 7 to 8, as a result of SEM analysis, it was found that the surface area was greatly increased, and as shown in FIG. 9, the white film was formed to have a thickness (C) of about 40 to 50 μm. I could confirm it.

 [Table 4]

Referring to Table 4, as a result of the EDS analysis, the ratio of C and N was not constant, and it was estimated that the material constituting the white film was an intermediate material in the process of converting silver into PSC.

As a result, it was confirmed that the best method in terms of improving the leaching rate of silver was to increase the amount of dissolved oxygen in the KCN solution by bubbling air to electrolyze the silver by electrochemical method. In addition, it was found that the cation exchange membrane is helpful for the synthesis of silver cyanide.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. These changes and modifications may be made without departing from the scope of the present invention. Accordingly, the scope of the present invention should be determined by the following claims.

120: potassium cyanide solution 120: cell
130: anode electrode 140: cathode electrode
150: cation exchange membrane 160: voltage

Claims (6)

(a) immersing a cathode electrode and a cathode electrode made of silver (Ag) in a cell in which potassium cyanide solution is stored; And
(b) applying a voltage to the cathode and anode electrodes of the cell to leach silver into the potassium cyanide solution;
In the step (b), the method of producing a PSC solution, characterized in that the air bubbling (Air Bubbling) to the cell is applied.
The method of claim 1,
In the step (b)
Method for producing a PSC solution, characterized in that the potassium cyanide solution is stirred.
The method of claim 1,
In the step (a)
And a cation exchange membrane (PEM) is further formed between the cathode electrode and the anode electrode.
The method of claim 1,
The step (b)
Method for producing a PSC solution, characterized in that carried out for 30 minutes to 2 hours.
The method of claim 1,
The cathode electrode
Method for producing a PSC solution, characterized by using an insoluble metal material for the potassium cyanide solution.
The method of claim 5,
The cathode electrode
Method for producing a PSC solution, characterized in that the stainless steel material.

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