KR101358428B1 - Apparatus for manufacture of metal cyanide solution with excellent leaching efficiency and manufacturing method of metal cyanide using the same - Google Patents

Abstract

Disclosed are a metal cyanide solution production apparatus excellent in leaching efficiency and a metal cyanide production method using the same.
Metal cyanide solution production apparatus according to the present invention includes a cell containing the cyan solution; Electrodes immersed in the cyan solution stored in the cell and having different polarities; And a voltage applying unit configured to apply a voltage to each of the electrodes of the cell, wherein the anode of the electrodes includes a metal component of a metal cyanide to be manufactured.

Description

Apparatus for producing a metal cyanide solution excellent in leaching efficiency and a method for producing a metal cyanide using the same

The present invention relates to a metal cyanide for plating, and more particularly, to a metal cyanide solution production apparatus excellent in leaching efficiency and a metal cyanide production method using the same.

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).

One object of the present invention is to provide an apparatus for preparing a metal cyanide solution which can increase the leaching efficiency compared to chemical leaching.

In addition, another object of the present invention to provide a metal cyanide manufacturing method through the electrochemical leaching and crystallization using the metal cyanide solution production apparatus.

Metal cyanide solution manufacturing apparatus according to the present invention for achieving the above object is a cell containing a cyanide (Cyanide) solution; Electrodes immersed in the cyan solution stored in the cell and having different polarities; And a voltage applying unit configured to apply a voltage to each of the electrodes of the cell, wherein the anode of the electrodes includes a metal component of a metal cyanide to be manufactured.

In addition, the metal cyanide manufacturing method according to the present invention for achieving the above another object comprises the steps of preparing a metal cyanide solution through the electrochemical leaching, using the metal cyanide solution manufacturing apparatus described above; And (b) inducing crystallization by reducing the solubility of the metal cyanide by cooling the metal cyanide solution.

Metal cyanide solution manufacturing apparatus according to the present invention by applying an electrochemical leaching process to increase the leaching rate of the metal component in the cyan solution compared to the chemical leaching it is possible to manufacture a metal cyanide solution excellent in leaching efficiency.

In addition, the metal cyanide solution manufacturing apparatus can increase the dissolution rate of the metal component by increasing the dissolution rate of the metal component in the cyan solution by applying air bubbling or stirring to the cyan solution.

In addition, the present invention can be easily produced metal cyanide through the electrochemical leaching and crystallization using the metal cyanide solution manufacturing apparatus.

1 is a formation chart of Au compounds using concentrations of cyan and voltage values.
2 is a view schematically showing an apparatus for preparing a metal cyanide solution according to the present invention.
Figure 3 is a flow chart for explaining a metal cyanide manufacturing method using a metal cyanide solution manufacturing apparatus according to the present invention.
4 is a graph showing the mass change of the gold electrode according to the leaching reaction time for each voltage of Examples 1 to 5 for the gold leaching process of the present invention.
5 is a graph showing the reaction rate according to the voltage of Examples 2 to 5 for the gold leaching process of the present invention.
6 is a graph showing the current density according to the reaction time of Examples 1 to 5 for the gold leaching process of the present invention.
7 is a graph showing the density according to the voltage of Examples 2 to 5 for the gold leaching process of the present invention.
8 is a graph showing the mass change of the silver electrode according to the leaching reaction time of Examples 1, 2 and Comparative Example for the silver leaching process of the present invention.
9 is a graph showing the amount of change in current according to leaching reaction time of Examples 1, 2 and Comparative Example for the silver leaching process of the present invention.
10 is a graph showing the dissolved oxygen amount according to leaching reaction time of Examples 1, 2 and Comparative Example for the silver leaching process of the present invention.

Hereinafter, an apparatus for preparing a metal cyanide solution and a method for preparing a metal cyanide using the same will be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

First, potassium cyanide (Potassium Gold Cyanide, KAu (CN) ₂ ) using a positive electrode made of gold (Au) or silver (Ag) according to the present invention; hereinafter referred to as 'PGC' and potassium cyanide (Potassium Silver Cyanide, The theoretical background for the synthesis of KAg (CN) ₂ hereinafter referred to as 'PSC' is described.

PGC  Theory of Synthesis

The dissolution reaction of very stable noble metals like Au can be thought of as split into two half cell reactions like electrochemical reactions.

Anode Reaction: Au + Au ⁺ + e, E ⁰ = -1.69V

       Cathode reaction:

In acidic solution, 2H ⁺ + 0.5O ₂ + 2e = H ₂ O, E ⁰ = 1.23 V

In alkaline _{solution, H 2 0 + 0.5O 2 -} 2e = 2OH -, E 0 = 1.23V

           Overall reaction in acidic solution

2Au + 2H ⁺ + 0.5O ₂ = 2Au ⁺ + H ₂ O, E ⁰ = -0.46V

The standard potential of the positive and negative reactions is lower than that of the negative electrode, so the standard potential of the positive reaction is -0.46V. Therefore, it can be seen that it is thermodynamically impossible to leach precious metals such as gold or silver by injecting oxygen gas in a simple acid solution. When the potential of the anodic reaction is expressed by the concentration of gold ions using the Nernst equation, the following equation [1] is used.

---- [식 1]

---- [Equation 1]

In other words, in order to reduce the potential of the anodic reaction of the gold leaching reaction, the activity of the gold ions generated by the dissolution of gold must be reduced. In general, cyan ions having a strong tendency to form complexes with gold ions are added to reduce the activity of gold ions. Decreases.

^{Au + + 2CN - = Au (} CN) 2 - ---- [ Formula 2]

Therefore, in the case of using NaCN solution to leach gold and silver can be represented by the total leaching reaction as shown in [Equation 3].

[Equation 3]

4Au = Au ^{+ +} 4e ^-

^{4Au + + 8CN - = 4Au (} CN) 2 -

_{2H 2 0 + O 2 + 4e} - = 4OH -

Before the ^{_{reaction: 4Au + O 2 + 8CN -}} + 2H 2 0 = 4Au (CN) 2 - + 4OH -

Cyan ions form HCN with hydrogen ions in aqueous solution. Therefore, it is necessary to adjust the cyan concentration according to the pH of the aqueous solution in order to set the proper conditions for leaching gold or silver using the blue water method. At this time, the cyan concentration required for leaching of gold can be obtained as shown in [Equation 5] below. First, the dissociation constant of HCN at 25 ° C. is as shown in Equation 4 below.

^---- [식 4]

^---- [Equation 4]

The total concentration of cyan in the leaching solution may be expressed as shown in [Formula 5] below.

---- [식 5]

---- [Equation 5]

If the concentration of gold is 2 g / t in the ore or waste containing gold, it is necessary to leach using Equation 5 above if the solution is leached under a pH of 9 to recover gold from these resources. The concentration of NaCN can be obtained as shown in Equation 6 below.

---- [식 6]

---- [Equation 6]

In the gold leaching reaction by NaCN, 2 moles of cyan ions are required to leach 1 mole (M) of gold, so that the concentration of cyan should be at least 0.02 M in order to set the concentration of gold ions to 0.01 M. Therefore, it can be seen from Equation 7 below that the concentration of NaCN necessary for leaching gold under these conditions is 0.04M. Converting the concentration of 0.04M NaCN to mass% is as follows.

---- [식 7]

---- [Equation 7]

In general, when the leaching of the gold content of 2g / t at pH 9, the concentration of NaCN is maintained at 0.1%, it can be seen that it fits well with the calculation results. On the other hand, by substituting [Equation 6] into the equation for the potential of the half reaction to the dissolution reaction of gold, it is possible to obtain a change in the dislocation reaction according to pH. As the pH of the solution increases from 0 to 9, the potential of the dissolution reaction decreases linearly and is constant in the pH range thereafter. Leaching gold.

According to Kirk's research group, Au is leached from the cyan solution to synthesize gold cyanide, and it is shown that the reaction consists of three steps of the following [Formula 8] to [Formula 10].

^{Au + CN - (adsorption) →} AuCN ads - ---- [ Equation 8]

^{_{AuCN ads - (oxidation) → AuCN}} ads + e - ---- [ Equation 9]

^{_{AuCN ads + CN - (dissolution)}} → Au (CN) 2 - ---- [ Equation 10]

When Au is leached to synthesize Au (CN) ₂ ⁻ , it can be seen that there is a movement of one equivalent of electrons. Using this result, the theoretical electrochemical equivalent is calculated to be 2.041 mg / C and 7.3476 g / hr.

Looking at the detailed reaction during the leaching reaction, it is known that oxygen is involved in this process. Habashi proposed the following reaction formulas and rate constants such as [Equation 11] and [Equation 12] where oxygen is supplied in the PGC synthesis reaction and hydrogen peroxide is produced in the product.

2Au + 4KCN + O ₂ + 2H ₂ O → 2KAu (CN) ₂ + 2KOH + H ₂ O ₂ ---- [Equation 11]

---- [식 12]

---- [Equation 12]

Jeffrey's team also suggests that oxygen is involved in the production of PGC by presenting the following reaction equation [13]. In addition, using the concentration of cyan and the voltage value as shown in Figure 1 proposed a formation chart of the Au compound in the region 1-5.

_{^{2Au + 4CN - + O 2 +}} 2H 2 O → 2Au (CN) 2 - + 2OH - + H 2 O 2 ---- [Equation 13]

PSC  Theory of Synthesis

When silver (Ag) reacts with cyanide (CN), Ag must have a monovalent oxidation number through electron exchange [Equation 14], and at a binding ratio of 1: 2, that is, Ag (CN) ₂ ^- is the most stable compound. It is known to form [Formula 15]. The process of leaching Ag into CN requires electron transfer, and it is common to involve two steps of reactions described in Equations 14 and 15 below.

^{Ag + CN - → AgCN + e} - ----- [ Equation 14]

^{AgCN + CN - → Ag (CN} ) 2 - ----- [ Equation 15]

In a more detailed analysis of the process, Habashi and Hiskey and others mentioned the need for oxygen in the silver leaching process. In one step, the release of electrons by leaching Ag into potassium cyanide solution is described in Eq. 14 ] Is the same as the reaction mechanism, but differs in the way oxygen absorbs electrons.

In high-purity Ag, four electrons by the Griffith model are adsorbed and reacted at the same time as shown in Equation 16 below. According to the Pauling model, two electrons are first adsorbed, and then a multistage reaction is carried out to adsorb two electrons again.

^{Ag + CN - → AgCN + e} - ---- [ Equation 14]

O _{2 ^{+ H 2 O + 4e - →}} 4OH - ---- [ Equation 16]

O _{2 ^{+ H 2 O + 2e - →}} HO 2 - + OH -, HO 2 - + H 2 O + 2e - → 3OH - ---- [ Equation 17]

Ag + 2KCN + 1 / 4O ₂ + 1 / 2H ₂ O → KAg (CN) ₂ + KOH --- [Equation 18]

In the course of the reaction described above, it can be seen that PSC is synthesized at the anode and OH ⁻ is formed at the cathode [Equation 18].

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.

2 is a view schematically showing an apparatus for preparing a metal cyanide solution according to the present invention.

Referring to FIG. 2, the metal cyanide solution manufacturing apparatus 100 according to the present invention may be immersed in a cell 120 containing the cyan solution 110 and a cyan solution 110 stored in the cell 120. And a voltage applying unit 150 for applying a voltage to each of the electrodes 130 and 140 having the polarity and the electrodes 130 and 140 of the cell 120. Anode Electrode (130) is composed of a metal component of the metal cyanide (Metal Cyanide) to be prepared.

In addition, the metal cyanide solution manufacturing apparatus 100 may further include a cation exchange membrane 160, an air bubbler 170, an agitator 180, and the like.

The cell 120 is an electrolytic cell for storing the metal cyanide solution to be prepared by receiving the cyan solution 110. The cell 120 may be formed of, for example, an acrylic material to minimize reactivity with the cyan solution 110. The size of the cell 120 is not particularly limited as long as it can accommodate the electrodes 130 and 140 having different polarities. For example, the cell 120 may be 135 mm × 100 mm × 90 mm.

Although not shown in the drawings, the cell 120 may further include a cover having an inlet for inserting and fixing the electrodes 130 and 140.

Here, the cyan solution 110 serves as an electrolyte, for example, potassium cyanide (hereinafter referred to as 'Potassium Cyanide'), which easily reacts with a metal component of a metal cyanide to be prepared to prepare a solution including a complex compound thereof. KCN ') solution can be used.

The cyan solution 110 is 1L of KCN solution of 2% by weight to 10% by weight of KCN dissolved in water (H ₂ O) so that leaching (leaching or eluting) of the metal component in the metal cyanide solution to be produced is active. Can be.

If the cyan solution 110 is less than 2% by weight, it is not possible to sufficiently secure the leaching amount of the metal component in the metal cyanide solution to be prepared. On the other hand, when the cyan solution 110 is more than 10% by weight, the cation remaining without increasing the metal component of the metal cyanide is increased, which may cause a material cost increase.

One of the electrodes 130 and 140 may be the anode electrode 130, and the other may be the cathode electrode 140.

The anode electrode 130 contributes to leaching the metal component of the metal cyanide to be prepared in the cyan solution 110. To this end, the anode electrode 130 includes a metal component of a metal cyanide to be manufactured, which preferably has a low specific resistance and can be precisely processed to design a precise circuit line. The anode electrode 130 may include, for example, a metal component made of gold (Au) or silver (Ag), and may be in a plate shape.

In contrast, the cathode electrode 140 is a counter electrode of the anode electrode 130, and an insoluble metal material for the cyan solution 110 is preferably used. The cathode electrode 140 may be, for example, a plate shape made of stainless steel (SUS).

The electrodes 130 and 140 may be fixed to the cyan solution 110 inside the cell 120 to be partially immersed. The electrodes 130 and 140 may be fixed by an inlet formed in the cover of the cell 110 or an electrode holder (not shown). It may be fixed by.

The voltage applying unit 150 directly applies a voltage to each of the electrodes 130 and 140 on the cyan solution 110 to induce ionization of the metal component of the anode electrode 130 to proceed with the cyanation reaction. The voltage applying unit 150 may include a wire (not shown) connecting the electrodes 130 and 140 of the cell 120 to each other.

In particular, the voltage applying unit 150 has a constant voltage within the range of 1.529V to 5V for each of the electrodes 130 and 140 of the cell 120 when the anode electrode 130 includes a metal component of silver (Ag). Can be applied. Preferably, the voltage applying unit 150 may apply a constant voltage at 2.5V to maintain the leaching rate of silver (Ag) in the cyan solution 110 or more.

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 19]), the standard reduction voltage of oxygen E ⁰ _[O] = 0.23 V, hydrogen standard reduction voltage E ⁰ _[H] = 0 V (see Equation 21). When the resistance (R) 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 20] and [Equation 21]).

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 19]

E ⁰ _{[ Ag ]} + E ⁰ _[O] + E ⁰ _[H] + R (resistance of solution) = 1.529 V ---- [Equation 20]

0.799V + 0.23V + 0V + 0.5V (50% of full voltage) = 1.529V --- [Equation 21]

On the contrary, when the anode electrode 130 includes a metal material of Au material, the voltage applying unit 150 changes the voltages applied within the range of 3.0V to 6.0V while the electrodes of the cell 120 are changed. Voltages that are varied may be applied to the respective ones 130 and 140.

At this time, when the voltage applied to the electrodes 130 and 140 by the voltage applying unit 150 is less than 3.0V, the leaching rate of the gold (Au) in the metal cyanide solution may be lowered. On the other hand, when the voltage applied to the electrodes 130 and 140 by the voltage applying unit 150 exceeds 6.0V, the leaching effect of gold Au may not be expected on the cyan solution 110.

In order to calculate the minimum voltage for Au electroleaching, the standard reduction electrode potential E ₀ of metal was calculated. At this time, E ⁰ _{[ Au ]} = 1.692 V of _Au (see [Equation 22]), E ⁰ _[O] = 0.23 V, and E ⁰ _[H] = 0 V (see [Equation 24]). The resistance (R) value of the cyan solution 110 was calculated as 50% of the total voltage, wherein the minimum voltage for Au electrolytic leaching was 2.0V (see [Equation 24]). Since this is a theoretical voltage, it is desirable to determine the initial voltage of the actual experiment to 2.5V.

Au = Au ⁺ + e-, E ⁰ _{[ Au ]} = 1.692 V ---- [Equation 22]

E _{0 [ Au ]} + E _{0 [O]} + E _{0 [H]} + R (resistance of solution) = 2V ---- [Equation 23]

1.692V + 0.23V + 0V + 0.9V (50% of total voltage) = 2V ---- [Equation 24]

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 positive electrode 130 to the negative electrode 140 through the cation exchange membrane 150.

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 metal cyanide solution manufacturing apparatus 100 may further include an air bubbler 170 in the cyan solution 110. The air bubbler 170 supplies the air and substantially oxygen to the cyan solution 110 stored in the cell 120 to react the cyanation reaction only with the anode electrode 130 including a metal component of silver (Ag). By increasing the speed, the dissolution rate of silver (Ag) in the cyan solution 110 may be increased to increase the leaching rate of silver (Ag) in the cyan solution 110.

The air bubbler 170 may generate air bubbles 175 to supply air to the cyan solution 110 in which the electrodes 130 and 140 are immersed. In particular, it is preferable to supply air to the cyan solution 110 including the anode electrode 130 participating in the cyanation reaction of the electrodes (130, 140).

As mentioned above, Habashi or Hiskey and others mentioned the need for oxygen in the leaching process of silver (Ag). Therefore, when air bubbling on the cyan solution 110 in the leaching process of silver (Ag) can increase the dissolution rate of silver (Ag) by increasing the dissolution rate of silver (Ag) in the cyan solution (110). .

Air bubbling of the cyan solution 110 using the air bubbler 170 is performed for 30 minutes to 2 hours to supply sufficient oxygen to the cyan solution 110 to achieve a dissolution rate of silver (Ag) of 100%. can do.

When air bubbling is performed in less than 30 minutes, the leaching rate of silver (Ag) in the cyan solution 110 may not be 100%. On the other hand, when the air bubbling is performed for more than 2 hours, the leaching effect of silver (Ag) in the cyan solution 110 may not be expected any more, and productivity may be lowered.

The air bubbler 170 may be provided inside the cell 120 as shown. Although not illustrated in the drawings, the air bubbler 170 may be provided outside the cell 120 to supply air to the cyan solution 110, and as long as the air can supply air to the cyan solution 110. The position of the bubbler 170 is not particularly limited.

The metal cyanide solution manufacturing apparatus 100 may further include a stirrer 180 that stirs the cyan solution 110 stored in the cell 120. The stirrer 180 is a component for improving the reaction rate of the cyanation reaction between the metal component of the positive electrode 130 and the cyan solution 110 by increasing the current intensity.

For example, the stirrer 180 may use a propeller type, a turbine type, a row type, a screw type, or the like. For example, as shown in Figure 2, the stirrer 180 is a cyan solution using a stirring drive coupled to the rotary drive unit 182, the rotary drive unit 182 to drive the rotation through a motor (motor), etc. It may be configured to include a support unit 186 coupled to the stirring unit 184 and the rotary driving unit 182 to support the rotary driving unit 182, but is not limited thereto and may be variously modified. have.

Metal cyanide solution manufacturing apparatus 100 according to the present invention by applying an electrochemical leaching process to increase the leaching rate of the metal component in the cyan solution 110 compared to chemical leaching it is possible to manufacture a metal cyanide solution excellent in leaching efficiency. . In addition, by applying air bubbling and / or stirring to increase the dissolution rate of the metal component in the cyan solution 110 may increase the leaching rate of the metal component.

Hereinafter, a metal cyanide manufacturing method using the metal cyanide solution manufacturing apparatus according to the present invention will be described.

Figure 3 is a flow chart for explaining a metal cyanide manufacturing method using a metal cyanide solution manufacturing apparatus according to the present invention.

Referring to FIG. 3, the metal cyanide manufacturing method according to the present invention includes preparing a metal cyanide solution through electrochemical leaching (S210) and inducing metal cyanide crystallization through cooling (S220).

In the step of preparing a metal cyanide solution through electrochemical leaching (S210), a metal cyanide solution through electrochemical leaching is prepared using the above-described metal cyanide solution manufacturing apparatus (see 100 of FIG. 2).

Specifically, in the step of preparing a metal cyanide solution through electrochemical leaching (S210) After connecting the electric wire to the cathode electrode 140 and the anode electrode 130 of gold (Au) or silver (Ag) material immersed in the cyan solution 110 stored in the cell 120, the anode from the voltage applying unit 150 A constant voltage is applied to each of the electrode 130 and the cathode electrode 140 to leach gold (Au) or silver (Ag) into the cyan solution 110 through a cyanation reaction. Then, PGC or PSC is synthesized in the anode electrode 130 in the course of the electrochemical electroleaching reaction according to the above-described theory of PGC or PSC synthesis.

In this case, when the anode electrode 130 is formed of gold (Au) material, the voltage applied within the range of 3.0V to 6.0V may be increased by changing the voltage so that the leaching speed of gold (Au) may be increased.

On the other hand, when the anode electrode 130 is formed of silver (Ag) material, it is possible to apply a constant voltage within the range of 1.529V to 5V. In particular, after applying a voltage to each of the electrodes (130, 140), air bubbling is performed for 30 minutes to 2 hours to supply sufficient oxygen to dissolve the silver (Ag) to the cyan solution 110, By increasing the reactivity, the leaching rate of silver (Ag) in the cyan solution 110 may be increased.

In addition, the metal component of the metal cyanide (eg, gold or silver) to be prepared in the cyan solution 110 by increasing the current intensity by stirring the cyan solution 110 in the step of preparing a metal cyanide solution through electrochemical leaching (S210). Of course, the leaching rate of) can be increased.

On the other hand, when the cation exchange membrane 160 is further formed between the anode electrode 130 and the cathode electrode 140, the cations left in the cathode electrolyte solution may be selectively permeated through the cation exchange membrane 160 to the cathode to be electrically connected with the OH ⁻ ions. By neutralizing this, the effect of controlling the equivalence ratio of the reaction system is possible.

Next, in the metal cyanide crystallization induction step (S220) through cooling, the metal cyanide solution is supersaturated using cooling to crystallize the metal cyanide.

When cooling the metal cyanide solution, supersaturation occurs due to a decrease in solubility, and thus metal cyanide may crystallize.

In this case, the metal cyanide may be crystallized with gold potassium cyanide (PGC) or silver potassium cyanide (PSC).

Thereafter, the crystallized metal cyanide may be dried to prepare a powdered metal cyanide.

Hereinafter, a method for preparing a PGC 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 gold plate of 50 mm × 150 mm size was used as the anode electrode, and a stainless steel sheet 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 4.0 wt% KCN solution (manufactured by Junsei) was used, and 500 ml was used for the anode chamber and 200 ml was used for the cathode chamber. After connecting wires to the electrodes of each chamber, a voltage of 2.5V was applied and reacted.

Example  2

The electrolytic leaching process of Au was carried out in the same manner as in Example 1 except that a voltage of 3V was applied.

Example  3

The Au electrolytic leaching process was performed in the same manner as in Example 1 except that a voltage of 4V was applied.

Example  4

The electrolytic leaching process of Au was carried out in the same manner as in Example 1 except that a voltage of 5 V was applied.

Example  5

The electrolytic leaching process of Au was carried out in the same manner as in Example 1 except that a voltage of 6 V was applied.

Character rating

<Amount of change in mass and current of Au electrode>

While the leaching reaction was performed for all or a part of Examples 1 to 5 for the gold leaching process, the change of the mass and current of the Au electrode according to the reaction time was measured, and the leaching of the initial mass after 60 minutes of the leaching reaction was performed. Rate and current efficiency are shown in Table 1 and Table 2, respectively.

At this time, the mass change amount of the Au electrode was investigated by using an inductively coupled plasma-spectral spectrometer (ICP-OES) Optima 7300DV (manufactured by PerkinElmer) after collecting the leachate during the leaching reaction. Was measured, and the results are shown in FIG. The current change amount of the Au electrode was measured using Vupower K3010 (manufactured by Aiken Co., Ltd.), and the results are shown in FIG. 5.

Hydrogen ion concentration and dissolved oxygen content

While the leaching reaction for a predetermined time to all or part of the gold leaching process Examples 1 to 5 using Orion 3 star (manufactured by Theromoscientific) in the KCN solution of each electrode to measure the hydrogen ion concentration according to the reaction time, Model 58 (Yellow Springs Instruments Co., Inc.) was used to determine the amount of dissolved oxygen over the reaction time.

<Concentration of Au Ion>

The concentration of gold (Au) ions in the positive electrode and negative electrode electrolyte solutions of Example 2 for the gold leaching process was measured, and the results are shown in Table 3.

Figure 4 is a graph showing the mass change of the gold electrode according to the leaching reaction time for each voltage of Examples 1 to 5 for the gold leaching process of the present invention, Figure 5 is a Example 2-5 for the gold leaching process of the present invention It is a graph showing the reaction rate according to the voltage, Table 1 below shows the leaching rate for the initial mass after 60 minutes of the leaching reaction for Examples 1 to 5 for the gold leaching process.

[Table 1]

Referring to FIG. 4 and Table 1, it can be seen that in Examples 1 to 5, as the voltage increases, the leaching rate of gold increases in proportion to the measured voltage. In particular, in the case of Example 5 to which a voltage of 6 V was applied, 163 mg of gold was leached per hour, and after 60 minutes, it was confirmed that 14.4% of the mass was leached compared to the initial mass. On the other hand, in Example 1 to which a voltage of 2.5V was applied, 2 mg of gold was leached per hour, and after 60 minutes, 0.81% of the mass was leached compared to the initial mass.

Referring to FIG. 5, when the regression analysis was performed for the Au leaching reaction rate according to the voltage in the range of 3V to 6V of Examples 2 to 5, each time the voltage was increased by 1V, the leaching amount per hour increased by 49.1 mg. Could.

4, 5 and Table 1, it can be seen that the leaching rate of gold can be increased by the method of boosting the voltage.

6 is a graph showing the current density according to the reaction time of Examples 1 to 5 for the gold leaching process of the present invention, Figure 7 is a density according to the voltage of Examples 2 to 5 for the gold leaching process of the present invention The graph shown.

Referring to FIG. 6, in Examples 1 to 5, the current value showed a constant pattern over time. Since the amount of gold leached relative to the total mass during the reaction, the surface area of the gold electrode was almost changed. It can be seen that the current amount is constant because

In particular, in the case of Example 5 to which the voltage of 6V was applied by increasing the voltage 2.4 times compared to Example 1 to which the 2.5V voltage was applied, it was confirmed that 52 times the current increased from 5.6mA to 292mA.

Referring to FIG. 7, when the regression analysis of the change in the average current amount according to the voltage in the range of 3V to 6V of Examples 2 to 5, it can be seen that each time the voltage increases by 1V, the current amount increases by 82mA / cm ² there was. That is, it can be seen that the current amount is sensitively changed by the voltage change.

The current density according to the voltage was obtained in the form almost similar to the graph of the mass change according to the voltage of FIG. Through this, it can be seen that the voltage and current amount are closely related, and it is confirmed that the current is an important factor in the change of leaching rate of gold.

Table 2 below shows the current efficiency for the initial mass after 60 minutes of the leaching reaction for Examples 1 to 5 for the gold leaching process.

[Table 2]

Referring to Table 2, when the current efficiency was calculated in Examples 1 to 5 compared to 2.041 mg / C, which is the theoretical electrochemical equivalent of gold, the current efficiency was generally low at 3.75 to 4.85% in the applied voltage range. This may be because the applied current was not used to leach gold, but was consumed to electrolyze water to generate oxygen and hydrogen.

Although not shown, when the amount of dissolved oxygen was measured in the course of the reaction, it was confirmed that the amount of dissolved oxygen increased with time. In the case of Example 5 to which the 6V voltage was applied, it was confirmed that dissolved oxygen increase was 3.6 times faster than Example 3 to which the 4V voltage was applied. That is, it can be seen that the amount of dissolved oxygen is increased by the electrolysis of water in the reaction process. Considering the current efficiency, it can be seen that most of the applied current was used to generate oxygen rather than leaching gold.

Table 3 below shows the concentration of gold (Au) ions in the positive electrode and negative electrode electrolyte solutions of Example 2 for the gold leaching process.

[Table 3]

Referring to Table 3, when the solution of the positive electrode and the negative electrode was taken and analyzed for the content of gold using ICP-OES, the positive electrode increased the gold content over time, but no gold was detected at the negative electrode. .

In other words, gold is eluted by an electrochemical method and reacted with cyan to form an anion complex. That is, it is thought that the anion complex did not pass through the cation exchange membrane, so it was not detected at the cathode.

As a result, it was confirmed that the method of boosting the voltage is the best method in terms of improving the leaching rate of gold in order to electrolyze gold by electrochemical method.

Hereinafter, the PSC solution preparation method according to the present invention will be described in detail by the following examples, but the present invention is not limited by 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, and 500 ml was used for the anode chamber and 200 ml was used for the cathode chamber.

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 Example 1, 2 and Comparative Examples for the silver leaching process, while changing the mass and current of the Ag electrode with the reaction time was measured for a certain time, the results are shown in Figures 8 and 9, respectively. . In addition, the electrochemical equivalents of Examples 1, 2 and Comparative Examples for the silver leaching process were calculated and shown in Table 4.

At this time, the mass change of the Ag electrode was measured by measuring the leaching amount of Ag through the analysis using the ICP-OES Optima 7300DV (manufactured by PerkinElmer) after the leaching solution during the leaching reaction. 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., the amount of dissolved oxygen according to the reaction time was measured, and the results are shown in Table 5 and FIG. 10, 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 6.

8 is a graph showing the mass change of the silver electrode according to the leaching reaction time of Examples 1, 2 and Comparative Examples of the silver leaching process of the present invention, Figure 9 is a first embodiment of the silver leaching process of the present invention And it is a graph showing the amount of change of the current according to the leaching reaction time of the comparative example.

Referring to FIG. 8, it was confirmed that the rate of dissolving the silver electrode in the KCN solution was the fastest compared to Example 2 and the comparative example. In Example 1, when 20 minutes had elapsed, 80.9% of the silver electrode was dissolved relative to the initial mass, and all the silver electrodes contained in the KCN solution were dissolved before 30 minutes had elapsed. 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 was found that oxygen in the air was involved in the reaction because the dissolution rate of the silver electrode dissolved in the KCN solution was faster in Examples 1 and 2 than the comparative example.

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. 9, 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.

And 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 4 below shows the calculated electrochemical equivalents in Examples 1, 2 and Comparative Examples for the silver leaching process of the present invention.

[Table 4]

Referring to Table 4, 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 is 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.

10 is a graph showing the dissolved oxygen amount according to leaching reaction time of Examples 1, 2 and Comparative Example for the silver leaching process of the present invention.

Referring to FIG. 10, in the case of Examples 1 and 2, it was found that the dissolved oxygen amount was kept constant in the state of about 2 to 3.5 ppm increase compared to Comparative Example 1, and the dissolved oxygen reduction ratio was small. This is consistent with the need for oxygen to dissolve silver, as Hiskey and Habasi mentioned.

Table 5 below shows the hydrogen ion concentration (pH) values in the KCN solution of each electrode according to leaching reaction time in Examples 1, 2 and Comparative Examples for the silver leaching process of the present invention.

[Table 5]

Referring to Table 5, in Examples 1, 2 and Comparative Examples, the positive electrode (+) had little pH change, 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 6 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 for the silver leaching process of the present invention.

TABLE 6

Referring to Table 6, in both 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. .

As a result, in order to electrolyze silver by electrochemical method, it was confirmed that it is the best method in terms of improving the leaching rate of silver by bubbling air to increase the dissolved oxygen in the KCN solution. 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.

100: metal cyanide solution production device
110: cyan solution 120: cell
130: anode electrode 140: cathode electrode
150: voltage application unit 160: cation exchange membrane
170: air bubbler 175: air bubbles
180: stirrer 182: rotary drive unit
184: stirring section 186: support section

Claims (15)

A cell containing cyan solution;
Electrodes immersed in the cyan solution stored in the cell and having different polarities; And
And a voltage applying unit configured to apply a voltage to each of the electrodes of the cell.
Among the electrodes, the anode electrode includes silver (Ag) or gold (Au),
Including the cation exchange membrane between the electrodes having different polarities, the cell is separated into a cathode chamber including a cathode electrode and a cathode chamber including a cathode electrode,
Metal cyanide solution manufacturing apparatus comprising an air bubbler for supplying air to the cyan solution.
delete delete delete The method of claim 1,
The voltage application unit
Metal cyanide solution production apparatus characterized by changing the applied voltage.
6. The method of claim 5,
The voltage application unit
Metal cyanide solution production apparatus, characterized in that for changing the voltage applied within the range of 3.0V to 6.0V.
delete The method of claim 1,
The metal cyanide solution manufacturing apparatus
Metal cyanide solution production apparatus characterized in that it further comprises a stirrer for stirring the cyan solution stored in the cell.
(a) preparing a solution of potassium cyanide or potassium cyanide via electrochemical leaching using the apparatus of claim 1; And
(b) inducing crystallization by reducing the solubility of the metal cyanide through cooling the metal cyanide solution;
In the electrochemical leaching, the electrolyte is cyan solution,
Metal cyanide manufacturing method characterized in that the air bubbling to supply air to the cyan solution.
delete delete delete 10. The method of claim 9,
In the step (a)
Metal cyanide manufacturing method characterized by using a voltage change.
14. The method of claim 13,
The voltage change is
Metal cyanide manufacturing method characterized in that the change within the range of 3.0V to 6.0V.
10. The method of claim 9,
In the step (a)
Method for producing a metal cyanide, characterized in that the cyan solution is stirred.

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