How to leach gold from copper anode mud

Extracting gold and silver from copper anode mud?

Extraction of gold and silver from copper anode mud

The process of enriching and recovering gold and silver from copper electrolytic anode mud is an important link to extract gold from metallurgical by-products. Copper anode mud is composed of many substances insoluble in electrolyte during electrolytic refining of copper anode, and its phase composition is complex. Among them, silver is mainly Ag, Ag2Se, Ag2Te, CuAgSe and AgCl, and gold is in (Ag, Au)Te2 or free state. The composition of copper anode mud varies from place to place. The general composition (ω/%) is: Cu 10 ~ 25, Au 0.5 ~ 5, Ag 5 ~ 30, Se 2 ~ 28, Te 0. 1 ~ 8, Pb1~ 25; In addition, it also contains a small amount of bismuth, antimony, arsenic, iron, Al2O3, SiO2, a small amount of palladium and platinum, with a water content of 20% ~ 40%. Pyrolysis-electrolysis method is often used to treat copper anode slime in large smelters, and leaching and wet treatment processes have been developed. Pyrolysis-electrolysis method is generally called traditional method.

Traditional craft? The technological process is basically the same as that of copper anode mud treatment, and the main processes are as follows: (1) sulfate roasting distillation to remove selenium, leaching roasting slag to remove copper; (2) the leaching residue is reduced and smelted to produce expensive lead alloy; (3) oxidizing and refining the lead-precious metal alloy into a gold-silver alloy, namely an anode plate; (4) silver electrolysis; (5) Pretreatment of silver anode mud, and then gold electrolysis. The traditional process is long and complicated, and the direct recovery rate of metal is not high, so a new process for treating copper anode slime has emerged. Although these new processes have replaced the traditional processes to some extent, they are still the improvement methods of the traditional processes in essence.

How to improve the traditional craft? There are low-temperature sulfation roasting-wet treatment, low-temperature oxidation roasting-wet treatment, sulfation roasting-wet precipitation of gold and silver, flotation enrichment of gold and silver, Sumitomo method and wet treatment. They can better protect the environment, shorten the production cycle, speed up the capital turnover and improve the economic benefits of enterprises. Anode mud contains a lot of copper, and removing copper in advance is beneficial to the extraction of gold and silver. Therefore, the new process improves the copper removal method to varying degrees.

The technological process of low-temperature sulfation roasting-wet treatment is shown in figure 1. The main process is as follows: (1) low-temperature sulfation roasting distillation of copper anode mud to remove selenium (573 ~ 953 k); (2) leaching the selenium removal residue after distillation with H2SO4+NaCl solution to remove copper; (3) leaching silver from the copper removal residue with ammonia water; (4) reducing the silver in the silver ammonia solution with hydrazine hydrate, and sending the obtained silver powder to silver electrolysis; (5) Na2CO3 is added into the stripping slag to convert chloride and sulfate of lead into lead carbonate, and then the stripping slag is stripped by nitric acid to obtain high-grade gold concentrate; (6) dissolving the gold concentrate with hydrochloric acid and Cl2, reducing the gold solution with SO2 to obtain coarse gold powder, sending the coarse gold powder to electrolytic gold, and replacing the reduced mother liquor with zinc powder to obtain palladium platinum concentrate; (7) The insoluble slag produced by chlorination of gold concentrate is sent to recover tin and antimony. The characteristic of this method is that the traditional lead smelting and pyrometallurgical refining processes are replaced by wet process, and the electrolytic refining operations such as sulfation roasting, distillation to remove selenium, leaching to remove copper and gold and silver are still retained. This improvement not only eliminates the harm of lead, shortens the treatment cycle, but also increases the direct yield of gold and silver from anode mud to electrolysis from 73% and 8 1% to 99.2% and 99% respectively.

The technological process of low-temperature oxidation roasting-wet treatment is shown in Figure 2. The main process is as follows: (1)648k low-temperature oxidation roasting oxidizes copper to CuO, Ag2Se to Ag2SeO3, and copper, selenium and tellurium are transformed into CuSO4, H2SO4 and H2SO4 by dilute sulfuric acid leaching, which are separated in solution; (2) firstly, the copper slag is chlorinated to separate gold, that is, NaClO3 is added into sulfuric acid medium, and gold, palladium and platinum are leached by stirring at the temperature of 353-363 K;

Then adjust the solution to pH 2 ~ 3, add oxalic acid to reduce gold, send the coarse gold powder to gold electrolysis or dissolution, and then extract and refine it. Replacing palladium and platinum with zinc powder or recovering palladium and platinum by solvent extraction in the mother liquor after reducing gold; (3) Under the conditions of pH8 and solid-liquid ratio 1: 8, the gold leaching residue was leached with a solution containing NaClO 3250 g/L for 3 hours, and silver generated Ag(SeO3)3- which entered the leaching solution. The leaching rate of silver is 99% ~ 99.8%, and the leaching solution contains about 50 g/L of silver, which is reduced by formaldehyde to obtain silver powder. The mother liquor can be recycled, and all the lead remains in the silver separation. The main advantage of this method is that the direct yield of gold and silver is high, which is 98.5% and 96% respectively. It is 12% and16% higher than the traditional method; Short production cycle and low treatment cost; Eliminate the harmful effects of lead and ammonia on the operating environment.

Sulfation roasting-wet precipitation of gold and silver? The process flow is shown in Figure 3, which mainly consists of sulfate roasting distillation to remove selenium, dilute sulfuric acid leaching and leaching residue dissolution to separate gold. (1) Sulfated roasting and distillation to remove selenium: roasting at sulfuric acid: anode mud = 1: 1 and 573K for 2 hours, and roasting at 823 ~ 873 K for 4 hours, the volatilization rate of selenium is over 99%, and the absorbed selenium is reduced to obtain crude selenium. (2) Dilute sulfuric acid leaching: at the solid-liquid ratio of 1:( 12 ~ 15) and the temperature of 353 ~ 363 K, the distilled selenium residue is leached with a solution containing sulfuric acid 1.5mol/L for 2 hours. The leaching rate of copper is 99%, the leaching rate of silver is 98%, and the leaching solution is replaced by copper. (3) Dissolving and separating gold from leaching residue: leaching gold-bearing leaching residue produced by leaching lead and tellurium from dilute sulfuric acid leaching residue with NaClO3 solution for 4 hours at the temperature of H2SO4 1.5 mol/L and NaCl 2 mol/L, with solid-liquid ratios of1:/Kloc-0 and 353-.

Enriching gold and silver by flotation? Both China and Japan use flotation to enrich gold and silver from copper anode slime. The method in China is to remove copper and selenium from anode slime, then grind it and then float it. Iron filings are added to replace silver in flotation, sulfuric acid is added to adjust the pH of the solution at the temperature of 348 ~ 353 K, metaphosphoric acid is added to inhibit gangue and lead, ethylene glycol, turpentine or methyl isobutyl methanol are used as foaming agents, butyl xanthate or black powder is used as collectors, and flotation is carried out in a medium with weak acidity to sulfuric acid content of 200 g/L, and the concentrate is obtained through primary roughing, secondary scavenging and secondary cleaning. The recovery rates of gold and silver reached 95.5% and 97.4% respectively, and 90% of lead remained in tailings. The selected concentrate is generally 50% of the original anode slime. Adding soda ash to the concentrate, smelting to obtain crude silver anode plate, and electrolyzing to obtain pure silver. Extraction of gold from silver electrolytic anode mud. The environmental pollution of flotation method is greatly improved compared with the original fire method, but the disadvantage is that the tailings contain higher gold and silver, which are 30 ~ 60g/t and 60 ~ 900g/t respectively.

Sumitomo law? The method used by Sumitomo Metal Mining Company of Japan. After drying, the copper anode mud was put into a 673K roasting furnace for oxidation roasting. After the feeding is completed, the temperature is raised to 793K within 65438 0 h, and then it is raised to 973K quickly, and kept at 65438 0 h. After fine grinding, it is leached with concentrated sulfuric acid at 353K with a solid-liquid ratio of 65,438+0: 5 for 3 hours. Gold and silver are leached from leaching residue by chlorination, silver chloride is precipitated from leaching solution by hydrochloric acid, and then sent to refining to extract gold. The direct yield of gold is over 98%. The obtained silver chloride is sent to refining to extract silver.

Wet treatment? The process is shown in Figure 4. The main process is as follows: (1) oxidizing and leaching with dilute sulfuric acid and air (or oxygen) to reduce copper, and returning the solution to copper electrolysis; (2) chlorine gas and sodium chlorate are used as oxidants in the copper slag, and only selenium and tellurium in the copper slag are leached by controlling the dosage of the oxidant, namely leaching potential, while gold, silver, palladium and platinum are not leached, and the leaching solution is sent to recover selenium and tellurium; (3) The leaching residue is NH. Oh or: Na. S0, leaching silver, and sending the silver leaching solution to silver for refining; (4) After removing lead from silver leaching residue with HNO3, dissolve gold with NaClO3 or Cl2 and hydrochloric acid, and send the gold solution to gold refining.