CN118028904B - A method for leaching precious metals by electrochemical oxidation of thiosulfate - Google Patents

Abstract

The invention discloses a method for leaching noble metals by thiosulfate electrochemical oxidation, which comprises the steps of taking a thiosulfate-electrolyte-alkali liquor system as electrolyte, adding noble metal materials into an anode chamber of an electrolytic tank, connecting a cathode and an anode arranged in the electrolytic tank with an external power supply, and leaching the noble metals by electrochemical oxidation; the electrolyte is a salt that does not include thiosulfate. The invention adopts the electrochemical thiosulfate method to extract noble metals, the leaching effect is superior to that of the existing copper ammonia technology, and the high-efficiency green extraction of noble metals (such as gold and silver) can be realized; not only avoiding the addition of a large amount of oxidizing agents such as copper, but also obviously reducing the consumption of thiosulfate radical while improving the leaching rate of noble metal, reducing the cost of leached medicament, further promoting the green sustainable development of noble metal industry and being easy to realize industrialized application.

Description

A method for leaching precious metals by electrochemical oxidation of thiosulfate

Technical Field

The invention relates to the technical field of hydrometallurgy, and in particular to a method for electrochemically oxidizing and leaching precious metals with thiosulfate.

Background Art

The cyanidation method is currently the most important method for gold extraction in the world due to its low cost and mature process. It uses an aqueous solution of alkali metal cyanide (KCN, NaCN) as a solvent to leach gold from gold mines in the presence of oxygen. However, cyanide is highly toxic, and its large-scale use will seriously harm the environment and human health, which is contrary to the current concept of green development. Thiosulfate is widely favored in the extraction of precious metals because of its advantages such as green and harmless, good selectivity, no corrosion to equipment, and mild leaching conditions. It is considered to be the most promising method for cyanide-free extraction of precious metals. At present, thiosulfate leaching of gold is mainly based on the copper ammonia-thiosulfate system. In this system, _O2 is used as an oxidant. By adding Cu2 ⁺ and ammonia to thiosulfate in an alkaline environment, the leaching rate of rare and precious metals can be increased. In this process, copper ions and ammonia form a relatively stable copper-ammonia complex ion Cu(NH ₃ ) ₄ ²⁺ , which can act as an oxidation catalyst to promote the formation of Au(NH ₃ ) ₂ ⁺ , significantly increasing the gold dissolution rate (18-20 times) and strengthening thiosulfate gold leaching. However, since E ^θ (Cu ²⁺ /Cu) and E ^θ (Cu(NH ₃ ) ₄ ²⁺ /Cu(S ₂ O ₃ ) ₃ ^5- )>E ^θ (S ₄ O ₆ ^2- /S ₂ O ₃ ^2- )>E ^θ (Au(NH ₃ ) ₂ ⁺ /Au ⁰ ) in the gold leaching system, and the diffusion coefficients of (Cu(NH ₃ ) ₄ ²⁺ and Cu ²⁺ are large and highly dispersed in the solution, thiosulfate is continuously oxidized and consumed, with a consumption of more than 50kg/t, which seriously restricts the industrial application of thiosulfate gold extraction technology.

In response to the above problems, in recent years, researchers have carried out a lot of research work around the problem of high consumption of thiosulfate leaching agents. At present, the main ways to reduce thiosulfate consumption are: basic reagent concentration control, adding stabilizers and developing non-copper ion leaching systems. For example, researchers have studied the formation of several different thiosulfate systems by adding additives (sodium chloride, ethylenediaminetetraacetic acid, carboxymethyl cellulose, sodium sulfite, etc.) or changing individual leaching reagents in the system (such as adding metallic iron, nickel and cobalt to form nickel ammonia, cobalt ammonia, iron oxalic acid systems). In addition, some scholars believe that the main reason for the high consumption of thiosulfate leaching agents is that most gold ores contain copper minerals. During the leaching process, copper ions are also continuously dissolved, resulting in a high concentration of copper ammonia complex ions in the solution. Therefore, it is proposed to add chelating agents such as disodium ethylenediaminetetraacetic acid (EDTA), amino acids, and carboxymethyl cellulose (CMC) to the leaching system to control the concentration of copper ammonia complex ions in the solution, thereby reducing the consumption of agents.

In the above method, when the cobalt ammonia-thiosulfate and nickel ammonia-thiosulfate systems are used to leach precious metals, the research results show that when Co(NH ₃ ) ₆ ³⁺ and Ni(NH ₃ ) ₆ ²⁺ are used as catalysts, the degree of oxidation and decomposition of thiosulfate is significantly reduced, and the lowest agent consumption can reach 1.2kg/t. However, due to the wide variety of complex ions formed by cobalt and nickel ions and ammonia molecules (Co(NH ₃ ) ₄ ²⁺ , Co(NH ₃ ) ₅ ²⁺ , Ni(NH ₃ ) ₂ ²⁺ , Ni(NH ₃ ) ₃ ²⁺ , Ni(NH ₃ ) ₄ ²⁺ , Ni(NH ₃ ) ₅ ^{2+ ,} etc.), the electrode potentials of different complex ions are different, resulting in unstable indicators for leaching precious metals. At the same time, the leaching mechanism of cobalt ammonia/nickel ammonia-thiosulfate is still unclear, and it is difficult to apply it in industry, and it is difficult to promote its application in a short period of time. Chandra et al. conducted a study on thiosulfate gold leaching using Fe ³⁺ as an oxidant and oxalate as a complexing agent. The results showed that the reagent consumption of the precious metal leaching system was low, but due to the poor complex stability of Fe(C ₂ O ₄ ) ^2- , when the solution pH was higher than 6.4, Fe(C ₂ O ₄ ) ^2- was converted into Fe(OH) ₃ precipitation, reducing the gold leaching efficiency. Under low pH conditions, thiosulfate will spontaneously decompose, and the reagent consumption will increase. In addition, the use of too many additives will increase the viscosity of the solution, causing the mineral powder to be unable to fully dissolve in water, and the opportunity for precious metals to contact with the reaction reagents will be reduced, resulting in poor metal leaching effects. In summary, the three methods of controlling the concentration of leaching reagents, adding stabilizers, and developing non-copper ion gold leaching systems can reduce the reagent consumption of thiosulfate gold leaching to a certain extent, but the three methods have strong limitations and cannot effectively take into account the efficiency of precious metal dissolution and leaching.

Therefore, in order to promote the replacement of green and environmentally friendly thiosulfate extraction of precious metals technology with cyanide extraction of precious metals, it is urgent to innovate thiosulfate extraction of precious metals technology, reduce the cost of leaching agents, and thereby promote the green and sustainable development of the precious metals industry.

Summary of the invention

In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for leaching precious metals with electrochemical oxidation of thiosulfate. The present invention uses an electrochemical oxidation method to replace the traditional copper ammonia oxidation method to solve the problem that the current thiosulfate leaching technology for precious metals is difficult to balance the reagent consumption and leaching efficiency.

To achieve the above object, the present invention is implemented through the following technical solutions:

A method for leaching precious metals by electrochemical oxidation of thiosulfate comprises: arranging a cation exchange membrane in an electrolytic cell, the cation exchange membrane dividing the electrolytic cell into an anode chamber and a cathode chamber; using a thiosulfate-electrolyte-alkali solution system as an electrolyte, adding precious metal materials into the anode chamber of the electrolytic cell, and connecting the cathode and anode arranged in the electrolytic cell to an external power supply to leach the precious metals by electrochemical oxidation; the electrolyte is an electrolyte that does not contain thiosulfate.

The biggest difference between the thiosulfate electrochemical oxidation method for extracting precious metals proposed in the present invention and the existing leaching technology is that no metal catalyst or complexing agent is used, that is, only thiosulfate-alkali solution is used, and electrolytes such as potassium chloride are used as the main electrolyte, and electrochemical anodic oxidation is performed to leach precious metals under the condition of power supply. This method not only has a good leaching effect, saves costs, allows the reuse of leaching solution, and significantly reduces the use of chemicals and the generation of secondary waste.

Preferably, the pH of the electrolyte is 7-13, more preferably pH=10.

Preferably, the concentration ratio of thiosulfate to electrolyte in the electrolyte is (0.1-0.5):(0.1-0.5).

Preferably, the thiosulfate is one or more of sodium thiosulfate, ammonium thiosulfate, and potassium thiosulfate.

Preferably, the alkali solution is one or more of ammonia water, sodium hydroxide and potassium hydroxide.

The alkali solution is further preferably ammonia water. When the alkali solution is ammonia water, the concentration ratio of thiosulfate, electrolyte and ammonia water in the electrolyte is (0.1-0.5): (0.1-0.5): (0.3-2.0).

Preferably, the electrolyte is one or more of chloride, sulfate, and carbonate.

Preferably, the chloride salt is one or both of potassium chloride and sodium chloride.

Preferably, a cation exchange membrane is provided in the electrolytic cell, and the cation exchange membrane separates the electrolytic cell into an anode chamber and a cathode chamber.

Preferably, the electrochemical condition is: the voltage is 0.3V to 3V.

More preferably, the electrochemical condition is: the voltage is 0.6V.

Preferably, the anode is platinum, titanium, copper, lead, glassy carbon, silicon carbide, stainless steel, graphite electrode or graphite felt, and the cathode is titanium, copper, stainless steel or graphite electrode.

The beneficial effects of the present invention are:

1. The present invention adopts the electrochemical thiosulfate method to extract precious metals, and the leaching effect is better than the existing copper ammonia technology, and can achieve efficient and green extraction of precious metals (such as gold and silver).

2. The present invention is simple to operate and easy to control, does not introduce other impurity ions, avoids the generation of waste liquid and waste gas, and reduces the recovery cost.

3. The present invention not only avoids the large-scale consumption of oxidants such as copper, but also significantly reduces the consumption of thiosulfate while improving the leaching rate of precious metals, reduces the cost of leaching agents, and thus promotes the green and sustainable development of the precious metal industry, and is easy to realize industrial application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a diagram showing the gold immersion effects of Example 1 and Comparative Example 1;

FIG2 is a diagram showing the silver immersion effects of Example 2 and Comparative Example 2;

Figure 3 is the consumption of thiosulfate after 24h of gold immersion in Example 1, Comparative Example 1 and Comparative Example 3;

Figure 4 is a diagram of the gold immersion effect under different systems;

FIG. 5 is a diagram showing the gold immersion effect under different voltage conditions of Example 3.

DETAILED DESCRIPTION

The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Electrochemical leaching is an emerging technology, which is favored by many scholars because of its green, high efficiency and avoidance of secondary pollution. Based on this, the present invention proposes a novel thiosulfate electrochemical oxidation method for extracting precious metals, including a thiosulfate-electrolyte-alkali solution system as an electrolyte, wherein the thiosulfate includes but is not limited to one or more of sodium thiosulfate, ammonium thiosulfate, and potassium thiosulfate, and the electrolyte may be one or two of chlorides, sulfates, and carbonates, preferably potassium chloride. The alkali solution may be one or more of ammonia water, sodium hydroxide, and potassium hydroxide, preferably ammonia water. In some embodiments, the concentration ratio of thiosulfate, electrolyte, and ammonia water in the electrolyte is (0.1-0.5): (0.1-0.5): (0.3-2.0). The pH of the electrolyte is 7-13, and more preferably pH=10.

The electrolytic cell is separated into an anode chamber and a cathode chamber by a cation exchange membrane, and precious metal materials are added to the anode chamber of the electrolytic cell. Platinum, titanium, copper, lead, glassy carbon, silicon carbide, stainless steel, graphite electrode or graphite felt are selected as anodes, and titanium, copper, stainless steel or graphite electrodes are selected as cathodes. They are placed in the anode chamber and cathode chamber respectively and connected to an external power supply. The precious metals are leached by electrochemical oxidation at a voltage of 0.3V to 3V.

The present invention provides a novel thiosulfate electrochemical oxidation leaching system. The method not only causes an electrochemical reaction to occur on the surface of mineral particles, but also utilizes an anode reaction to leach precious metals from the mineral. During the leaching process, the metal mineral collides with the anode and loses electrons, undergoes electrochemical oxidation and direct dissolution (electrochemical corrosion), and the reaction formula is as follows:

Au-e- ^→ Au ⁺

Ag-e ^- →Ag ⁺

Thiosulfate forms complexes with metal ions (Au ⁺ , Ag ⁺ )

Au ⁺ +2S ₂ O ₃ ^2- =Au(S ₂ O ₃ ) ₂ ^3-

Ag ⁺ +2S ₂ O ₃ ^2- =Ag(S ₂ O ₃ ) ₂ ^3-

The presence of ammonia in the system can prevent the insoluble products (such as elemental sulfur) generated by thiosulfate during the dissolution of precious metals from being deposited on the mineral surface. At the same time, the formation of the complex Au( _{S2O3 )} ( _NH3 ) ^- , Ag( _{S2O3 )} ( _NH3 ) ^- can prevent the oxidation/disproportionation of unstable thiosulfate. Therefore, the alkali solution of the present invention is preferably ammonia water.

Therefore, in the present invention, no other chemical oxidants and complexing agents need to be added, and the leaching process is safer and more cost-effective. This method allows the leaching solution to be reused, significantly reducing the use of chemicals and the generation of secondary waste.

In the technical solution provided by the present invention, an electrochemical reaction occurs on the surface of the mineral particles, and the anodic reaction is used to leach the metal in the mineral. The liquid phase in the electrolytic cell is both a leaching agent for the mineral raw material and an electrolyte. The leaching of the metal in the mineral raw material is a dual effect of the chemical leaching of the mineral raw material by the leaching agent and the electrochemical leaching of the anodic reaction. The cation exchange membrane plays a role in isolating the cathode area and the anode area, preventing non-metallic particles in the anode area from entering the cathode area, and also preventing gold/silver thiosulfate complex ions from entering the cathode area, thereby affecting the determination of the leaching amount.

The present invention is described in detail below with reference to specific embodiments.

The cation exchange membrane used in the electrolysis system of the following examples was purchased from Shandong Tianwei, model: EDCIS.

Example 1

The electrolyte composition of the S ₂ O ₃ ^2- -KCl-NH ₃ system is: 0.3 M Na ₂ S ₂ O ₃ , 0.2 M KCl, 0.5 M ammonia water, and the initial pH is adjusted to 10 with saturated NaOH.

The electrolytic cell is separated into two chambers, the positive and negative, by a cation exchange membrane to prevent the gold complex anions from entering the cathode and thus affecting the determination of the leaching amount. The prepared electrolyte is poured into the electrolytic cell to keep the liquid levels of the positive and negative chambers level. The gold powder concentration in the anode chamber is 333 mg/L. The pre-moistened graphite felt is used as the anode, and the polished titanium plate is used as the cathode. Then the power supply is connected, the voltage is set to 0.6 V, and the speed is adjusted to 900 rpm for gold leaching. Samples are taken at different times, and the concentration of precious metal gold leaching of samples at different time points is detected by atomic absorption spectrometry. The concentration of thiosulfate in the leachate (i.e., electrolyte) after leaching for 24 hours is titrated by iodine titration to calculate its consumption.

Comparative Example 1

The reaction electrolyte of _S2O32 ^--KCl _{- NH3} system was prepared in the same manner as in Example 1, and then the electrolytic cell was separated into anode and cathode chambers by a cation exchange membrane to prevent the gold complex anion from entering the cathode and thus affecting the determination of the leaching amount. The prepared electrolyte was poured into the electrolytic cell to keep the liquid levels of the cathode and cathode chambers level. The gold powder concentration in the anode chamber was 333 mg/L, and the rotation speed was adjusted to 900 rpm without power. The samples were taken at different times, and the leaching concentration of precious metal gold of the samples at different time points was detected by atomic absorption spectrometry. The concentration of thiosulfate in the leachate (i.e., electrolyte) after leaching for 24 hours was titrated by iodine titration to calculate its consumption.

Figure 1 is a comparison chart of gold leaching in the _{S2O32 --} ^KCl - _NH3 system with and without power on in Example 1 and Comparative Example 1. It can be seen that the gold concentration measured in the _{S2O32 --} ^KCl - _NH3 system with power on for 24 hours is 80.9 mg/L, while the gold concentration measured in the S2O32--KCl-NH3 system with power on for 24 hours is 0.315 mg/L, which is equivalent to no leaching, indicating that power on effectively promotes gold leaching.

Example 2

The reaction electrolyte of S ₂ O ₃ ^2- -KCl-NH ₃ system was prepared in the same manner as in Example 1, and then the electrolytic cell was separated into anode and cathode chambers by a cation exchange membrane to prevent the silver complex anions from entering the cathode and thus affecting the determination of the leaching amount.

The gold powder concentration in the anode chamber was 333 mg/L. The pre-moistened graphite felt was used as the anode, and the polished titanium plate was used as the cathode. The power supply was then connected, the voltage was set to 0.6 V, and the speed was adjusted to 900 rpm for silver leaching. Samples were taken at different times, and the concentration of precious metal silver leaching of samples at different time points was detected by atomic absorption spectroscopy.

Comparative Example 2

The precious metal silver was leached in a method substantially the same as that in Example 2, except that no electricity was applied during the silver leaching process, and samples were taken at different times, and the concentration of precious metal silver leached from the samples at different time points was detected by atomic absorption spectroscopy.

Figure 2 is a comparison of the silver leaching effects of the _{S2O32 --} ^KCl - _NH3 system with and without electricity in Example 2 and Comparative Example 2. It can be seen that the concentration of silver leached for 24 hours measured under the condition of electricity in the _{S2O32 --} ^KCl - _NH3 system is 58.5 mg/L, and the concentration of silver leached for 24 hours without electricity is 20.1 mg/L, indicating that electricity can promote the leaching of silver to a great extent.

Comparative Example 3

The leaching solution composition of the S ₂ O ₃ ^2- -Cu ²⁺ -NH ₃ system was: 0.3 M Na ₂ S ₂ O ₃ , 1 mM CuSO ₄ , 0.5 M ammonia water, and the initial pH was adjusted to 10 with saturated NaOH.

The electrolytic cell is separated into two chambers, anode and cathode, by a cation exchange membrane to prevent gold complex anions from entering the cathode and thus affecting the determination of the leaching amount. The prepared leachate is poured into the electrolytic cell to keep the liquid levels of the cathode and cathode chambers level. The gold powder concentration in the anode chamber is 333 mg/L. Without power, the speed is adjusted to 900 rpm for gold leaching, and samples are taken after 24 hours. The leaching concentration of precious metal gold is detected by atomic absorption spectrometry. The concentration of thiosulfate in the leachate (i.e., electrolyte) after 24 hours of leaching is titrated by iodine titration to calculate its consumption.

Figure 3 shows the consumption of thiosulfate after 24 hours of gold immersion in Example 1, Comparative Example 1 and Comparative Example 3. It can be seen that the consumption of S ₂ O ₃ ^2- after power-on is similar between Example 1 and Comparative Example 1, while the consumption of S ₂ O ₃ ^2- by the traditional copper ammonia oxidation method in Comparative Example 3 is significantly increased, indicating that the electrochemical oxidation method provided by the present invention can reduce the consumption of reagents while immersing gold.

Comparative Example 4

The leaching solution composition of the S ₂ O ₃ ^2- -Cu ²⁺ -KCl-NH ₃ system was: 0.3 M Na ₂ S ₂ O ₃ , 0.2 M KCl, 1 mM CuSO ₄ ·5H ₂ O, 0.5 M ammonia water, and the initial pH was adjusted to 10 with saturated NaOH.

The electrolytic cell is separated into anode and cathode chambers by a cation exchange membrane to prevent gold complexed anions from entering the cathode and affecting the determination of the leaching amount. The prepared leaching solution is poured into the electrolytic cell to keep the liquid levels of the cathode and cathode chambers level. The gold powder concentration in the anode chamber is 333 mg/L. Without power, the speed is adjusted to 900 rpm for gold leaching. Samples are taken after 24 hours, and the leaching concentration of precious metal gold is detected by atomic absorption spectrometry.

Figure 4 is a diagram of the gold leaching effects under different systems. It can be seen that the gold concentration of the _{S2O32 --} ^KCl - _NH3 system in Example 1 under the condition of electrical leaching for 24 hours is 80.9 mg/L, the gold concentration of the _{S2O32 --} ^{Cu2 +} _-NH3 system (copper ammonia system) in Comparative Example ₃ is 27.999 mg/L, and the gold concentration of the S2O32 _-- ^{Cu2 +} -KCl- _NH3 system in Comparative Example 4 is 36.693 mg/L. The results show that the copper ammonia system does not have as good a leaching effect as the electrochemical system of the present invention.

Example 3

The reaction electrolyte of S ₂ O ₃ ^2- -KCl-NH ₃ system was prepared in the same manner as in Example 1, and then the electrolytic cell was separated into anode and cathode chambers by a cation exchange membrane to prevent the gold complex anions from entering the cathode and thus affecting the determination of the leaching amount.

The gold powder concentration in the anode chamber was 200 mg/L. The pre-moistened graphite felt was used as the anode, and the polished titanium plate was used as the cathode. The power supply was then connected, and the voltages were set to 0V, 0.3V, 0.6V, 0.9V and 1.2V for five parallel experiments. The rotation speed was adjusted to 900 rpm, and the atomic absorption spectrometry was used to detect the leaching concentration of precious metal gold after 24 hours.

Figure 5 is a comparison of the gold leaching effects of the S ₂ O ₃ ^2- -KCl-NH ₃ system under different voltage conditions. It can be seen that with the increase of voltage, the gold concentration first increases, then decreases, and then increases again. The leaching effect is best when the applied voltage is 0.6V, and the thiosulfate consumption is also less at this time.

In summary, the present invention uses an electrochemical oxidation method to replace the traditional copper ammonia oxidation method, and oxidizes and dissolves precious metals through electrochemical anodic oxidation at low voltage, without the need to add other oxidants or complexing agents (such as Cu ²⁺ ), making the leaching process safer and more cost-effective. This method allows the reuse of the leachate, significantly reduces the use of chemicals and the generation of secondary waste, achieves green and efficient leaching of precious metals while reducing the consumption of reagents, and solves the problem that the current thiosulfate gold leaching technology is difficult to balance the consumption of reagents and leaching efficiency.

It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims (8)

1. The method for leaching the noble metal by the thiosulfate electrochemical oxidation is characterized by comprising the following steps of:

A cation exchange membrane is arranged in the electrolytic tank, and divides the electrolytic tank into an anode chamber and a cathode chamber; adding electrolyte into the cathode chamber and the anode chamber, wherein the electrolyte consists of thiosulfate, electrolyte and alkali liquor, adding noble metal materials into the anode chamber of the electrolytic tank, connecting a cathode and an anode arranged in the electrolytic tank with an external power supply, and leaching noble metal through electrochemical oxidation; the electrolyte is one or two of potassium chloride and sodium chloride; the alkali liquor is ammonia water.

2. The method for the electrochemical oxidative leaching of noble metals by thiosulfate according to claim 1, characterized in that the pH of the electrolyte is 7-13.

3. The method for the electrochemical oxidative leaching of noble metals by thiosulfate according to claim 1, wherein the concentration ratio of thiosulfate to electrolyte in the electrolyte is (0.1-0.5): (0.1 to 0.5).

4. The method for the electrochemical oxidative leaching of noble metals by thiosulfate according to claim 1, characterized in that the thiosulfate is one or more of sodium thiosulfate, ammonium thiosulfate and potassium thiosulfate.

5. The method for the electrochemical oxidative leaching of noble metals by thiosulfate according to claim 4, wherein the concentration ratio of thiosulfate, electrolyte and ammonia water in the electrolyte is (0.1-0.5): (0.1 to 0.5): (0.3 to 2.0).

6. The method for the electrochemical oxidative leaching of noble metals from thiosulfates in accordance with claim 1, wherein the electrochemical oxidation conditions are: the voltage is 0.3V-3V.

7. The method for the electrochemical oxidative leaching of noble metals from thiosulfates in accordance with claim 6, wherein the electrochemical oxidation conditions are: the voltage is 0.6V.

8. The method for the electrochemical oxidative leaching of noble metals from thiosulfate according to claim 1, wherein the anode is platinum, titanium, copper, lead, glassy carbon, silicon carbide, stainless steel, graphite electrode or graphite felt and the cathode is titanium, copper, stainless steel or graphite electrode.