A method for preferentially extracting gold and silver from lead anode slime

Abstract

The application provides a method for preferentially extracting gold and silver from lead anode slime, and relates to the technical field of precious metal recovery. First, valuable metals such as silver and antimony in the lead anode slime are leached into a solution by catalytic oxidation leaching in the presence of a protective agent, and gold is enriched in the residue. Then, silver is selectively precipitated from the leaching solution to obtain silver precipitation residue and valuable metal solution. Finally, the valuable metals in the solution are recovered by adding a neutralizing agent and a precipitating agent, and the obtained leaching mother liquor can be returned to leaching after supplementing hydrochloric acid. The valuable metal precipitation is used for recovering antimony and bismuth. The method changes the traditional lead anode slime treatment idea of'removing impurities first and then refining', has the characteristics of high direct recovery rate of gold and silver (>99.5%), fast reaction speed (total consumption time <1 h), low cost and no waste residue and waste water, and is expected to solve the problems of long gold and silver recovery process, low direct recovery rate, capital accumulation and difficult treatment of arsenic and antimony-containing flue dust in the existing lead anode slime treatment method. The method has significant economic and environmental benefits and good application prospect.

Description

Technical Field

[0001] This invention relates to the field of precious metal recycling technology, and in particular to a method for preferentially extracting gold and silver from lead anode mud. Background Technology

[0002] Lead anode slime is produced during the electrolytic process of lead smelting. It contains precious metals such as antimony, bismuth, arsenic, lead, copper, tellurium, selenium, and tin. The vast majority of gold and silver in the lead smelting system are concentrated in the anode slime. The gold content in lead anode slime is approximately 0.002%–0.8%, and the silver content is approximately 0.1%–25%. Gold and silver account for 60%–90% of the value of lead anode slime, making it an important raw material for gold and silver extraction and a significant source of profit for lead smelters. Currently, the strategic importance and application value of gold and silver are continuously increasing, attracting more and more attention. Therefore, improving the gold and silver recovery efficiency from lead anode slime is of profound significance for enhancing my country's resource security capabilities.

[0003] The currently widely used industrial method for treating lead anode sludge is "reduction smelting-oxidation blowing-gold and silver refining," which has high processing capacity and low cost, but suffers from problems such as high energy consumption, significant loss of gold and silver in the slag, arsenic-containing dust pollution, and a poor working environment. Although some studies have improved equipment and processes, the problem of gold and silver loss in large quantities of smelting slag and dust has not been solved. Wet processing usually utilizes the chemical inertness of precious metals, first removing valuable metals through a series of pretreatments to obtain precious metal concentrates, and then refining the precious metals. The controlled electrochlorination leaching-chlorination gold separation process has problems with long pretreatment time and loss of Ag in the leaching solution, while the alkaline leaching for arsenic removal-acid leaching for impurity removal process has problems with long process flow and high reagent costs.

[0004] Current processing methods place gold and silver extraction at the end of the process, resulting in lengthy pretreatment and impurity removal times. This leads to a prolonged gold and silver recovery process (several days), low direct recovery rates (Au ~97%, Ag ~92%), and significant capital tied up. Therefore, developing a method for the preferential and efficient extraction of gold and silver from lead anode mud is of great significance. Summary of the Invention

[0005] This invention solves the problems of long gold and silver recovery process, low direct gold and silver recovery rate, serious capital backlog, high energy consumption, arsenic-containing dust pollution, and poor working environment in existing lead anode mud treatment technologies by improving the process.

[0006] Specifically, a method for preferentially extracting gold and silver from lead anode mud includes: S1. Catalytic Oxidative Leaching: A protective agent is added to a solution containing hydrochloric acid, chloride salts, and catalytic metal ions. After mixing with lead anode mud, an oxidizing gas is introduced for leaching. After leaching, the solution is filtered to obtain gold-rich slag and leachate. Without the protective agent, gold leaching will result in loss. The role of chloride salts is to provide the leaching agent and maintain the selective oxidizing property of copper, because the required chloride concentration for leaching is relatively high. Without the addition of chloride salts, the acidity of the system will be too high.

[0007] S2, Selective silver precipitation: Add iodide to the leachate obtained in S1 to recover silver. After the reaction is complete, filter to obtain silver iodide slag and valuable metal solution. S3, Hydrolysis / Precipitation: Neutralizing agent and precipitating agent are added sequentially to the valuable metal solution obtained in S2 to precipitate the valuable metal in the solution, resulting in valuable metal precipitate and leaching mother liquor. The leaching mother liquor is replenished with hydrochloric acid and then returned to catalytic oxidation leaching. The valuable metal precipitate is used to recover antimony and bismuth.

[0008] Preferably, the chloride salt in step S1 is one or more of sodium chloride, calcium chloride, and ammonium chloride, and the catalytic metal ion is copper ion or cuprous ion, specifically copper chloride or cuprous chloride.

[0009] Preferably, the protective agent in step S1 is a metal or intermetallic compound, preferably metallic tellurium, metallic selenium, or tellurium selenide (wherein the ratio of selenium to tellurium can be any common ratio), and the amount used is greater than 0 and does not exceed 0.2% of the mass of the lead anode mud.

[0010] Preferably, in step S1, the leachate contains H + The concentration of the catalyst is 0.5–3 mol / L, the concentration of the catalytic metal ion is 2–20 g / L, the total chlorine concentration is adjusted to 200–260 g / L using chloride salt, the reaction temperature is 80–100 °C, and the liquid-solid ratio is 8:1–20:1. Under these process conditions, gold can be enriched by more than 30 times in one step, and the reaction time is less than 1 hour.

[0011] Preferably, the oxidizing gas in step S1 is selected from air and / or oxygen. The amount of gas introduced only needs to meet the requirements of the oxidation reaction, and there are no special requirements.

[0012] Preferably, in step S1, the leaching rates of silver, antimony, bismuth, arsenic, and lead are all higher than 99.5%, and the leaching rate of gold is lower than 0.5%; the slag ratio (i.e., the ratio of the weight of the leached slag to the weight of the raw material, which can reflect the enrichment multiple of gold) is lower than 4%, and the main component of the gold-rich slag is SiO2.

[0013] Preferably, the iodide in step S2 is one or more of sodium iodide, calcium iodide, zinc iodide, magnesium iodide, lead iodide, antimony iodide, and bismuth iodide.

[0014] Preferably, in step S2, the amount of iodide used is 1.1 to 1.3 times the molar amount of silver, the reaction temperature is 0 to 100°C, and the reaction time is 0.5 to 1 h.

[0015] Preferably, the neutralizing agent used in step S3 is one or more of sodium hydroxide, ammonia, calcium hydroxide, calcium oxide, calcium carbonate, and water. It is more preferable to use at least two of them, and more preferably, at least one of sodium hydroxide, ammonia, calcium hydroxide, calcium oxide, and calcium carbonate is used in combination with water as a neutralizing agent. The precipitant is one or more of sodium sulfide, sodium hydrosulfide, hydrogen sulfide, calcium sulfide, and ammonium sulfide.

[0016] Preferably, in step S3, the final pH value after adding the neutralizing agent is 1.0~1.7, and the amount of sulfide added is 1.05~1.2 times the total molar amount of residual metal. By using such process conditions, it is possible to avoid both excessively high acidity leading to the production of too much hydrogen sulfide and excessively low acidity hindering the reuse of the leachate.

[0017] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: This invention can preferentially extract gold and silver from lead anode mud, enriching gold by more than 30 times in one step in less than 1 hour, with a direct gold recovery rate of over 99.5%, and the resulting gold slag can be directly refined. The second step achieves selective silver extraction, with impurity metal content in the silver slag less than 10%, and a direct silver recovery rate also greater than 99.5%. It can directly process fresh anode mud without pre-oxidation. The oxidant consumed is air / oxygen, which improves reaction efficiency while reducing oxidation costs. The purified leaching mother liquor can be recycled to treat lead anode mud, avoiding the generation of high-salt and heavy metal-containing wastewater and reducing costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0020] The technical solution of this invention is described below.

[0021] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0022] In this embodiment of the invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the difference, their intended meanings are consistent. Similarly, the terms "of," "corresponding," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the difference, their intended meanings are consistent.

[0023] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0024] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0025] The lead anode mud used in the examples comprises at least the following components: Au 60 g / t, Ag 4.09%, Sb 42.18%, Bi 17.12%, As 6.30%, Pb 13.65%, Te 0.28%, and Se 0.03%. Au and Ag are mainly present in elemental form, while the other metals are in elemental form and low-valence oxides.

[0026] Example 1

[0027] A method for preferentially extracting gold and silver from lead anode mud includes: preparing H2O using water, concentrated hydrochloric acid, sodium chloride, and cuprous chloride. +A leachate with a concentration of 0.5 mol / L cuprous ions, 2 g / L cuprous ions, and 240 g / L Cl was prepared. Tellurium was added at 0.2% of the lead anode mud mass. The lead anode mud was leached with oxygen at 80 °C and a liquid-to-solid ratio of 15:1 for 17 min. The leaching rates of silver and valuable metals were both above 99.5%, while the gold leaching rate was only 0.3% (i.e., a gold recovery rate of 99.7%). The slag ratio was 3.2%, and the gold enrichment factor in the slag was 31 times. The leachate was immediately filtered and transferred to a new reactor. 1.1 times the theoretical amount of sodium iodide was added, and the reaction was carried out at room temperature for 30 min, followed by filtration to obtain a solution of silver iodide and valuable metals. The silver precipitation rate was 99.7%. 0.5 g / L sodium hydroxide was added to the valuable metal solution, and water was added to adjust the pH to ~1.5. Then, 8 g / L sodium sulfide was added, and the reaction was continued for 1 minute. After filtration, valuable metal slag and purified liquid were obtained, with the precipitation rate of valuable metals exceeding 98%.

[0028] Example 2

[0029] A method for preferentially extracting gold and silver from lead anode mud includes: preparing H2O using water, concentrated hydrochloric acid, calcium chloride, and copper chloride. + A leachate with a concentration of 3 mol / L copper ions, 5 g / L copper ions, and 300 g / L Cl was used. The amount of selenium added was 0.1% of the lead anode mud mass. The lead anode mud was leached with oxygen at 85 °C and a liquid-to-solid ratio of 12:1 for 16 min. The leaching rates of silver and valuable metals were both above 99.5%, while the gold leaching rate was only 0.4% (i.e., a gold recovery rate of 99.6%). The slag ratio was 3.3%, and the gold enrichment factor in the slag was 30 times. The leachate was immediately filtered and transferred to a new reactor. 1.2 times the theoretical amount of zinc iodide was added, and the reaction was carried out at room temperature for 30 min, followed by filtration to obtain a solution of silver iodide and valuable metals. The silver precipitation rate was 99.9%. 6 g / L calcium oxide was added to the valuable metal solution, and water was added to adjust the pH to ~1.1. Then, 10 g / L sodium sulfide was added, and the reaction was continued for 1 minute. After filtration, valuable metal slag and purified liquid were obtained, with the precipitation rate of valuable metals being greater than 98%.

[0030] Example 3

[0031] A method for preferentially extracting gold and silver from lead anode mud includes: preparing H2O using water, concentrated hydrochloric acid, ammonium chloride, and copper chloride. +A leachate with a concentration of 2 mol / L copper ions, 15 g / L copper ions, and 260 g / L Cl was used. Tellurium selenide was added at 0.01% of the lead anode mud mass. The lead anode mud was leached with air at 95 °C and a liquid-to-solid ratio of 10:1 for 15 min. The leaching rates of silver and valuable metals were both above 99.5%, while the gold leaching rate was only 0.4% (i.e., a gold recovery rate of 99.6%). The slag ratio was 2.9%, and the gold enrichment factor in the slag was 34 times. The leachate was immediately filtered and transferred to a new reactor. 1.2 times the theoretical amount of calcium iodide was added, and the reaction was carried out at room temperature for 30 min, followed by filtration to obtain a solution of silver iodide and valuable metals. The silver precipitation rate was 99.9%. 4 g / L calcium oxide was added to the valuable metal solution, and water was added to adjust the pH to ~1.3. Then, 9 g / L sodium sulfide was added, and the reaction was carried out at room temperature for 1 minute. After filtration, valuable metal slag and purified liquid were obtained, with the precipitation rate of valuable metals being greater than 98%.

[0032] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preferentially extracting gold and silver from lead anode mud, characterized in that, include: S1. Catalytic oxidation leaching: A protective agent is added to a solution containing hydrochloric acid, chloride salts and catalytic metal ions. After mixing with lead anode mud, an oxidizing gas is introduced for leaching. After leaching, the solution is filtered to obtain gold-rich slag and leachate. The catalytic metal ion is selected from copper ions and / or cuprous ions; the protective agent is a metal or intermetallic compound, selected from metal tellurium, metal selenium, and tellurium selenide; S2, Selective silver precipitation: Add iodide to the leachate obtained in S1 to recover silver. After the reaction is complete, filter to obtain silver iodide slag and valuable metal solution. S3, Hydrolysis / Precipitation: Neutralizing agent and precipitating agent are added sequentially to the valuable metal solution obtained in S2 to precipitate the valuable metal in the solution, resulting in valuable metal precipitate and leaching mother liquor. The leaching mother liquor is replenished with hydrochloric acid and then returned to catalytic oxidation leaching. The valuable metal precipitate is used to recover antimony and bismuth.

2. The method according to claim 1, characterized in that, The chloride salt in step S1 is one or more of sodium chloride, calcium chloride, and ammonium chloride.

3. The method according to claim 1, characterized in that, In step S1, H in the leachate + The concentration of the catalyst is 0.5~3 mol / L, the concentration of the catalytic metal ion is 2~20 g / L, the total chlorine concentration is adjusted to 200~260 g / L using chloride salt, the reaction temperature is 80~100 ℃, and the liquid-solid ratio is 8:1~20:

1.

4. The method according to claim 1, characterized in that, In step S1, the leaching rates of silver, antimony, bismuth, arsenic, and lead are all higher than 99.5%, the leaching rate of gold is lower than 0.5%, and the slag rate is lower than 4%.

5. The method according to claim 1, characterized in that, The iodide in step S2 is one or more of sodium iodide, calcium iodide, zinc iodide, magnesium iodide, lead iodide, antimony iodide, and bismuth iodide.

6. The method according to claim 1, characterized in that, In step S2, the amount of iodide used is 1.1 to 1.3 times the molar amount of silver, the reaction temperature is 0 to 100 °C, and the reaction time is 0.5 to 1 h.

7. The method according to claim 1, characterized in that, The neutralizing agent used in step S3 is one or more of sodium hydroxide, ammonia, calcium hydroxide, calcium oxide, and calcium carbonate; the precipitating agent is one or more of sodium sulfide, sodium hydrosulfide, hydrogen sulfide, calcium sulfide, and ammonium sulfide.

8. The method according to claim 1, characterized in that, After adding the neutralizing agent in step S3, the final pH value is 1.0~1.7, and the amount of sulfide added is 1.05~1.2 times the total molar amount of residual metal.

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