Method for stepwise dissolving out copper, selenium and tellurium in copper anode slime and enriching precious metal

Abstract

The invention discloses a method for stepwise dissolution of copper, selenium and tellurium in copper anode slime and enrichment of precious metals, the method comprises the steps of ball milling and drying, pressure leaching, oxygen pressure conversion and alkaline leaching, in the pressure leaching process, the oxygen partial pressure in a sulfuric acid solution with the concentration of 10-30 g / L is controlled to be 0.05-0.2 MPa at the temperature of 100-120 DEG C, NaCl and HCl are added in the oxygen pressure conversion to improve the Se recovery rate, and the alkaline leaching is carried out at the temperature of 100-120 DEG C; na2S is added in alkaline leaching, so that the tellurium recovery rate is remarkably improved, and the copper-selenium-tellurium leaching efficiency is high.

Description

Technical fields:

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a method for the graded leaching and enrichment of copper-selenium-tellurium precious metals in copper anode mud. Background technology:

[0002] Copper anode mud is a product of the copper electrolytic refining process, containing various valuable metals such as copper, selenium, tellurium, gold, and silver.

[0003] Based on the composition and phase characteristics of copper anode slime, the purpose of anode slime treatment is to maximize the recovery of precious metals while recovering other valuable metals as much as possible. The general process flow for anode slime treatment mainly includes pretreatment, pyrometallurgical processes, hydrometallurgical processes, and precious metal purification processes. The purpose of the pretreatment process is to remove impurity metals from the anode slime that are detrimental to subsequent processes using different methods, and to produce precious metal-enriched slag. The copper anode slime pretreatment process mainly involves the removal of metals such as copper, selenium, and tellurium. Industrialized methods mainly include sulfation roasting, pressurized oxidative leaching in a sulfuric acid system, and chlorination leaching.

[0004] Sulfation roasting involves mixing copper anode slime with concentrated sulfuric acid and roasting it in a rotary kiln at 450–550°C. This oxidizes selenium into volatile SeO2, which is then recovered as crude selenium, while copper is converted into soluble copper sulfate. Sulfation roasting offers advantages such as high selenium and copper removal rates (greater than 97%). However, it suffers from low tellurium recovery (less than 50%), high energy consumption, and a tendency to cause SO2 pollution.

[0005] The sulfuric acid system pressurized oxidation leaching mainly uses high temperature and high pressure to enhance the leaching of copper in copper anode mud. In this process, the copper leaching rate reaches more than 98%, and the process is simple and the processing time is short. However, it has high requirements for pressurized leaching equipment, and the selenium and tellurium leaching rates are low, with the selenium leaching rate being less than 30% and the tellurium leaching rate being about 50%.

[0006] Chlorination leaching involves adding an oxidant to a sulfuric acid and sodium chloride system for oxidative leaching. Commonly used oxidants include chlorine, sodium chlorate, and manganese dioxide. Although chlorination leaching can effectively remove selenium and tellurium from copper anode mud, it has disadvantages such as the dispersion of precious metals and high oxidant consumption. Summary of the Invention:

[0007] The purpose of this invention is to provide a method for the graded leaching and enrichment of copper selenium tellurium in copper anode mud.

[0008] This invention is achieved through the following technical solutions:

[0009] A method for the graded leaching and enrichment of copper-selenium-tellurium precious metals in copper anode mud, characterized by comprising the following steps:

[0010] (1) Ball milling and drying: The copper anode mud is ball milled to 100% pass through a 100-mesh sieve and then dried in a forced-air drying oven at 100℃ for 4-8 hours; the copper anode mud is a product of the copper electrolytic refining process, and based on a total mass percentage of 100%, it contains Cu 10-30wt.%, Se 1-15wt.%, Te 0.5-10wt.%, Au 0.01-0.5wt.%, and Ag 0.1-2wt.%, of which copper mainly exists in the form of Cu2Se, CuSeO3, CuO, etc., and tellurium mainly exists in the form of Cu2Te, Ag2Te, etc.

[0011] (2) Pressure leaching: The copper anode mud dried in step (1) is leached in a sulfuric acid solution with a concentration of 10-30 g / L, preferably 10-20 g / L, at a liquid-to-solid ratio of 4-10 mL / g, preferably 4-5 mL / g, at 100-120°C, preferably 105-115°C, with an oxygen partial pressure of 0.05-0.2 MPa, preferably 0.05-0.1 MPa, for 2-4 hours. After leaching, the liquid and solid are separated to obtain copper sulfate leaching solution and pressure leaching residue.

[0012] (3) Oxygen pressure conversion: Prepare a NaCl conversion solution with a concentration of 1-5 g / L, preferably 2-4 g / L, adjust the pH to 3.0-4.0 with hydrochloric acid, add the pressure leaching residue obtained in step (2) to the solution at a liquid-to-solid ratio of 4-10 mL / g, preferably 6-8 mL / g, mix well, and put it into a high-pressure reactor. After oxygen pressure conversion for 2-4 hours at a temperature of 120-150℃, preferably 135-150℃, an oxygen partial pressure of 0.2-0.5 MPa, preferably 0.4-0.5 MPa, and a stirring speed of 200-600 rpm, the liquid and solid are separated to obtain a selenite solution and oxygen pressure conversion residue;

[0013] (4) Alkaline leaching: Prepare a leaching solution with NaOH concentration of 20-80 g / L (preferably 40-60 g / L) and Na2S concentration of 10-20 g / L (preferably 10-15 g / L). Add the oxygen pressure conversion residue obtained in step (3) to the solution at a liquid-to-solid ratio of 4-10 mL / g (preferably 4-5 mL / g) and mix well. Leach for 2-4 hours at a temperature of 60-90℃ (preferably 70-80℃) and a stirring speed of 200-600 rpm. After liquid-solid separation, obtain sodium tellurite solution and precious metal concentrate.

[0014] The main chemical reaction equations involved in this invention are as follows:

[0015] Pressure leaching: CuO + H₂SO₄ = CuSO₄ + H₂O

[0016] CuSeO3 + H2SO4 = CuSO4 + H2SeO3

[0017] Cu2Se+2H2SO4+O2=2CuSO4+Se↓+2H2O

[0018] Cu2Te+2H2SO4+2O2=2CuSO4+TeO2↓+2H2O

[0019] Oxidative transformation: Ag₂Se + 2HCl + 1.5O₂ = H₂SeO₃ + 2AgCl↓

[0020] Ag2Te+2HCl+2O2=TeO2↓+2AgCl↓+H2O

[0021] Se + H₂O + O₂ = H₂SeO₃

[0022] Alkaline leaching: TeO2 + 2NaOH = Na2TeO3 + H2O

[0023] Compared with traditional methods, the present invention has the following advantages:

[0024] 1) The present invention provides a stepwise leaching method for copper, selenium, and tellurium from copper anode mud, comprising ball milling and drying, pressure leaching, oxygen pressure conversion, and alkaline leaching steps. The pressure leaching process is controlled by maintaining the oxygen partial pressure at 0.05–0.2 MPa in a sulfuric acid solution with a concentration of 10–30 g / L at 100–120 °C. NaCl and HCl are added during the oxygen pressure conversion to improve the Se recovery rate. Na2S is added during the alkaline leaching to significantly improve the tellurium recovery rate. This method features high copper, selenium, and tellurium leaching efficiency.

[0025] 2) The copper sulfate solution obtained by this invention can be returned to the copper electrolysis system, and the selenite and sodium tellurite solutions can be directly reduced to prepare crude selenium and crude tellurium, avoiding the lengthy separation process of copper, selenium and tellurium in the traditional process.

[0026] 3) The precious metals do not dissolve at all during the process of this invention, and the subsequent precious metal extraction process is simple. Detailed implementation method:

[0027] The following is a further description of the invention, but not a limitation thereof.

[0028] In all embodiments of the present invention, copper anode mud obtained from the electrolytic refining process of a certain copper smelting enterprise was selected for the stepwise leaching of copper selenium tellurium. The copper anode mud was dried, ball-milled, and sieved until 100% of the particles passed through a 100-mesh sieve, then mixed and dried for 6 hours. The contents of Cu, Se, and Te in the copper anode mud were analyzed to be 19.80 wt.%, 8.48 wt.%, and 2.50 wt.%, respectively. Copper mainly exists in the form of Cu2Se, CuSeO3, CuO, etc., and tellurium mainly exists in the form of Cu2Te, Ag2Te, etc.

[0029] Example 1:

[0030] Pressure leaching (stage 1): The dried copper anode mud was leached for 2 hours in a sulfuric acid solution with a sulfuric acid concentration of 10 g / L, a temperature of 105℃, a liquid-to-solid ratio of 5 mL / g, and an oxygen partial pressure of 0.1 MPa. After liquid-solid separation, copper sulfate leaching solution and pressure leaching residue were obtained.

[0031] Oxygen pressure conversion (two stages): Prepare a conversion solution with a NaCl concentration of 2 g / L, adjust the pH to 4.0 with hydrochloric acid, add the pressure leaching residue at a liquid-to-solid ratio of 6 mL / g, mix well, and place in an autoclave. After 2 hours of oxygen pressure conversion at a temperature of 135℃, an oxygen partial pressure of 0.4 MPa, and a stirring speed of 200 rpm, separate the liquid and solid to obtain a selenite solution and oxygen pressure conversion residue.

[0032] Alkaline leaching (three stages): Prepare a leaching solution with a NaOH concentration of 40 g / L and a Na2S concentration of 10 g / L. Add oxygen pressure conversion residue to the solution at a liquid-to-solid ratio of 5 mL / g, mix well, and leach for 2 hours at a temperature of 70℃ and a stirring speed of 200 rpm. After liquid-solid separation, obtain sodium tellurite solution and precious metal concentrate.

[0033] Example 2:

[0034] Pressure leaching (stage 1): The dried copper anode mud was leached for 3 hours in a sulfuric acid solution with a sulfuric acid concentration of 15 g / L, a temperature of 110℃, a liquid-to-solid ratio of 4 mL / g, and an oxygen partial pressure of 0.1 MPa. After liquid-solid separation, copper sulfate leaching solution and pressure leaching residue were obtained.

[0035] Oxygen pressure conversion (two stages): Prepare a conversion solution with a NaCl concentration of 2.5 g / L, adjust the pH to 3.5 with hydrochloric acid, add the pressure leaching residue at a liquid-to-solid ratio of 7 mL / g, mix well, and place in an autoclave. After oxygen pressure conversion for 3 hours at a temperature of 140℃, an oxygen partial pressure of 0.4 MPa, and a stirring speed of 400 rpm, separate the liquid and solid to obtain a selenite solution and oxygen pressure conversion residue.

[0036] Alkaline leaching (three stages): Prepare a leaching solution with a NaOH concentration of 40 g / L and a Na2S concentration of 12 g / L. Add oxygen pressure conversion residue to the solution at a liquid-to-solid ratio of 5 mL / g, mix well, and leach for 3 hours at a temperature of 80℃ and a stirring speed of 400 rpm. After liquid-solid separation, obtain tellurite solution and precious metal concentrate.

[0037] Example 3

[0038] Pressure leaching (stage 1): The dried copper anode mud was leached for 3 hours in a sulfuric acid solution with a sulfuric acid concentration of 20 g / L, a temperature of 115℃, a liquid-to-solid ratio of 5 mL / g, and an oxygen partial pressure of 0.15 MPa. After liquid-solid separation, copper sulfate leaching solution and pressure leaching residue were obtained.

[0039] Oxygen pressure conversion (two stages): Prepare a conversion solution with a NaCl concentration of 3 g / L, adjust the pH to 3.0 with hydrochloric acid, add the pressure leaching residue at a liquid-to-solid ratio of 7 mL / g, mix well, and place in an autoclave. Under the conditions of 150℃, oxygen partial pressure of 0.5 MPa, and stirring speed of 500 rpm, oxygen pressure conversion is carried out for 2 hours. After liquid-solid separation, sodium selenite solution and oxygen pressure conversion residue are obtained.

[0040] Alkaline leaching (three stages): Prepare a leaching solution with a NaOH concentration of 60 g / L and a Na2S concentration of 15 g / L. Add oxygen pressure conversion residue to the solution at a liquid-to-solid ratio of 5 mL / g, mix well, and leach for 2 hours at a temperature of 80℃ and a stirring speed of 400 rpm. After liquid-solid separation, obtain sodium tellurite solution and precious metal concentrate.

[0041] Comparative Example 1:

[0042] The experimental conditions for this comparative example are basically the same as those for Example 1, except that no oxygen was introduced during the pressure leaching process.

[0043] Comparative Example 2:

[0044] The experimental conditions for this comparative example are basically the same as those for Example 1, except that the sulfuric acid concentration is 100 g / L during the pressure leaching process.

[0045] Comparative Example 3:

[0046] The experimental conditions for this comparative example are basically the same as those for Example 1, except that pure water was used in the oxygen pressure conversion process without the addition of NaCl and HCl.

[0047] Comparative Example 4:

[0048] The experimental conditions for this comparative example are basically the same as those for Example 1, except that Na2S was not added during the alkaline leaching process, only NaOH was used.

[0049] The results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0050] Table 1

[0051]

[0052] A comparison of Example 1 and Comparative Example 1 shows that the lack of O2 during pressurized leaching leads to a decrease in copper recovery rate.

[0053] A comparison of Example 1 and Comparative Example 2 shows that the use of high-concentration sulfuric acid in the pressure leaching process causes some selenium and tellurium to dissolve in the first stage of pressure leaching, resulting in a decrease in selenium recovery rate in the subsequent second stage of oxygen pressure conversion and a decrease in tellurium recovery rate in the third stage of alkaline leaching.

[0054] A comparison of Example 1 and Comparative Example 3 shows that adding NaCl and HCl during oxygen pressure conversion improves the Se recovery rate in the second-stage oxygen pressure conversion. A comparison of Example 1 and Comparative Example 4 shows that adding Na2S during alkaline leaching significantly improves the tellurium recovery rate in the third-stage alkaline leaching.

Claims

1. A method for the graded leaching and enrichment of precious metals, including copper, selenium, and tellurium, in copper anode mud, characterized in that... The method includes the following steps: (1) Ball milling and drying: The copper anode mud is ball milled until 100% passes through a 100-mesh sieve and then dried in a forced-air drying oven at 100℃ for 4-8 hours; the copper anode mud is a product of the copper electrolytic refining process, and based on a total mass percentage of 100%, it contains Cu 10-30wt.%, Se 1-15wt.%, Te 0.5-10wt.%, Au 0.01-0.5wt.%, and Ag 0.1-2wt.%, of which copper mainly exists in the form of Cu2Se, CuSeO3, and CuO, and tellurium mainly exists in the form of Cu2Te and Ag2Te; (2) Pressure leaching: The copper anode mud dried in step (1) is leached in a sulfuric acid solution with a concentration of 10-30 g / L at a liquid-to-solid ratio of 4-10 mL / g for 2-4 h at 100-120 °C and an oxygen partial pressure of 0.05-0.2 MPa. After liquid-solid separation, copper sulfate leaching solution and pressure leaching residue are obtained. (3) Oxygen pressure conversion: Prepare a NaCl conversion solution with a concentration of 1-5 g / L, adjust the pH to 3.0-4.0 with hydrochloric acid, add the pressure leaching residue obtained in step (2) at a liquid-to-solid ratio of 4-10 mL / g, mix well, and put it into a high pressure vessel. Under the conditions of 120-150℃, oxygen partial pressure of 0.2-0.5 Mp, and stirring speed of 200-600 rpm, oxygen pressure conversion is carried out for 2-4 hours. After liquid-solid separation, selenite solution and oxygen pressure conversion residue are obtained. (4) Alkaline leaching: Prepare a leaching solution with NaOH concentration of 20-80 g / L and Na2S concentration of 10-20 g / L. Add the oxygen pressure conversion residue obtained in step (3) to the solution at a liquid-to-solid ratio of 4-10 mL / g, mix well, and leach for 2-4 hours at a temperature of 60-90℃ and a stirring speed of 200-600 rpm. After liquid-solid separation, obtain sodium tellurite solution and precious metal concentrate.

2. The method according to claim 1, characterized in that, Step (2) is as follows: The copper anode mud dried in step (1) is leached in a sulfuric acid solution with a concentration of 10-20 g / L at a liquid-to-solid ratio of 4-5 mL / g for 2-4 hours at 105-115℃ and an oxygen partial pressure of 0.05-0.1 MPa. After liquid-solid separation, copper sulfate leaching solution and pressure leaching residue are obtained.

3. The method according to claim 1, characterized in that, Step (3) Oxygen pressure conversion: Prepare a NaCl conversion solution with a concentration of 2-4 g / L, adjust the pH to 3.0-4.0 with hydrochloric acid, add the pressure leaching residue obtained in step (2) at a liquid-to-solid ratio of 6-8 mL / g, mix well, and put it into a high-pressure reactor. Under the conditions of 135-150℃, oxygen partial pressure of 0.4-0.5 MPa, and stirring speed of 200-600 rpm, oxygen pressure conversion is carried out for 2-4 hours. After liquid-solid separation, selenite solution and oxygen pressure conversion residue are obtained.

4. The method according to claim 1, characterized in that, Step (4) alkaline leaching is as follows: Prepare a leaching solution with a NaOH concentration of 40-60 g / L and a Na2S concentration of 10-15 g / L. Add the oxygen pressure conversion residue obtained in step (3) to the solution at a liquid-to-solid ratio of 4-5 mL / g, mix well, and leach for 2-4 hours at a temperature of 70-80℃ and a stirring speed of 200-600 rpm. After liquid-solid separation, sodium tellurite solution and precious metal concentrate are obtained.

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