Chlorine-free and dore-free silver anode slime full-wet treatment process

Abstract

The present application relates to the technical field of rare and precious metal extraction, and particularly relates to a full-wet treatment process for silver anode slime without chlorine and without gold separation residue, which comprises the following steps: mixing silver anode slime with chlorine-free leaching agent, liquid-solid ratio is 8-12:1, leaching at 75-85 DEG C for 3-5h, after filtration separation, obtaining gold-containing leaching residue and silver-palladium-containing leaching solution; adding palladium precipitation reagent to the silver-palladium-containing leaching solution, adjusting pH value to 1.5-2.5, reacting at 55-65 DEG C for 1.5-2.5h, filtering to obtain palladium precipitate and palladium precipitation post-solution; adding silver precipitation reagent to the palladium precipitation post-solution, adjusting pH value to 2-3, reacting at 40-50 DEG C for 1-2h, reducing silver ions in the solution into silver element precipitate, filtering to obtain silver precipitate and silver precipitation post-solution; after dissolving the silver precipitate, adding it into silver electrolysis system to supplement electrolyte silver ions; at the same time, purifying the silver precipitation post-solution, removing impurity ions and recycling it as leaching agent; carrying out gold separation treatment on the gold-containing leaching residue, obtaining high-purity gold product. The present application completely avoids gold separation residue by abandoning chlorine-containing reagent throughout the whole process.

Description

Technical Field

[0001] This invention relates to the field of rare and precious metal extraction technology, specifically to a fully wet process for treating silver anode mud without chlorine or gold-separating slag. Background Technology

[0002] Silver anode slime, a key secondary resource in the gold and silver refining process, is rich in rare and precious metals such as gold, silver, platinum, and palladium, and has extremely high recycling value. Currently, the mainstream industrial processing technology mostly adopts the hydrochloric acid pre-leaching-sodium chlorate hydrochloric acid gold separation process. In this process, hydrochloric acid pre-leaching allows base metals and some palladium to enter the liquid phase, while gold, silver, platinum, and palladium remain in the solid phase. During the gold separation stage, sodium chlorate and hydrochloric acid are added to dissolve gold, platinum, and palladium, while silver is converted into silver chloride precipitate (i.e., gold separation sludge).

[0003] However, traditional processes have many prominent problems: gold-separating slag is difficult to dissolve in water and acid, making washing extremely difficult and requiring multiple return processes, resulting in a surge in the amount of gold and silver slag used and low processing efficiency; when gold-separating slag is returned to the alloying process for pyrometallurgical treatment, the process is slow and difficult, causing the gold and silver content in the smelting slag to increase and the recovery rate to decrease significantly; the use of chlorine-containing reagents will severely corrode production equipment, furnace bricks and flues, increasing equipment maintenance costs and safety risks; at the same time, gold-separating slag is a hazardous waste, with high treatment costs and a high risk of secondary pollution.

[0004] Existing improved processes still have significant drawbacks: some companies use chlorine or hydrochloric acid pre-leaching, which still generates a large amount of gold-separating sludge that needs to be returned to the furnace via pyrometallurgical processes, resulting in low silver recovery rates and the need for additional electrolyte preparation to replenish silver; other processes, after nitric acid pre-leaching, still require the addition of chloride salts to generate silver chloride precipitate, making the process cumbersome and resulting in low palladium recovery rates. For example, patent CN106065434B discloses a comprehensive silver anode mud recovery process, which achieves multi-metal recovery, but still relies on a chlorine-containing system to complete silver separation, inevitably generating gold-separating sludge, and failing to solve core issues such as equipment corrosion, process occupancy, and hazardous waste treatment. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a fully wet process for treating silver anode mud without chlorine or gold-separating slag.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A fully wet process for treating silver anode slime without chlorine or gold-separating slag includes the following steps:

[0008] (1) Chlorine-free selective leaching: Silver anode mud is mixed with chlorine-free leaching agent at a liquid-solid ratio of 8-12:1 and leached at 75-85℃ for 3-5 hours. After filtration and separation, gold-containing leaching residue and silver-palladium-containing leaching solution are obtained. The chlorine-free leaching agent is a nitric acid solution with a concentration of 2.5-3.5 mol / L.

[0009] (2) Stepwise palladium precipitation: Add palladium precipitation reagent to the silver-palladium leaching solution obtained in step (1), adjust the pH value to 1.5-2.5, react at 55-65℃ for 1.5-2.5h, filter to obtain palladium precipitate and palladium precipitation solution; the palladium precipitation reagent is dimethylglyoxime, and the molar ratio of the amount of palladium precipitation reagent added to palladium in the silver-palladium leaching solution is 1.2-1.5:1;

[0010] (3) Chlorine-free silver precipitation: Add silver precipitation reagent to the palladium precipitation solution obtained in step (2), adjust the pH value to 2-3, react at 40-50℃ for 1-2 hours to reduce the silver ions in the solution to silver elemental precipitate, filter to obtain silver precipitate and silver precipitation solution; the silver precipitation reagent is sodium bisulfite, and the molar ratio of the amount of silver precipitation reagent added to the silver in the palladium precipitation solution is 1.1-1.3:1;

[0011] (4) Electrolyte replenishment and purification: After dissolving the silver precipitate obtained in step (3), add it to the silver electrolysis system to replenish the electrolyte silver ions; at the same time, purify the silver precipitation liquid obtained in step (3), remove impurity ions, and return it to step (1) as a leaching agent for recycling.

[0012] (5) Gold recovery: The gold-containing leaching residue obtained in step (1) is subjected to gold separation treatment to obtain high-purity gold products.

[0013] Further, in step (1), the silver anode mud is pretreated before leaching. The pretreatment includes crushing and grinding to make the particle size of the silver anode mud ≤100 mesh. After grinding, it is dried at 105-110℃ for 2-3 hours.

[0014] Further, in step (2), the palladium precipitate is washed, dried, and then calcined at 700-800℃ for 2-3 hours to obtain crude palladium powder. The crude palladium powder is then refined to obtain a palladium product with a purity of ≥99.95%.

[0015] Further, in step (3), the silver precipitate is washed and then dissolved in nitric acid to obtain a silver nitrate solution. After the silver nitrate solution is filtered to remove insoluble impurities, it is directly added to the silver electrolysis system.

[0016] Further, in step (4), the purification treatment step of the silver precipitation liquid includes: adding chelating resin to the silver precipitation liquid, adjusting the pH value to 4.5-5.5, and reacting at 55-65℃ and stirring rate of 150-200r / min for 1-1.5h; the amount of chelating resin added is 5%-8% of the volume of the silver precipitation liquid.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention provides a chlorine-free and gold-separating sludge-free wet process for treating silver anode mud. The process involves chlorine-free selective leaching, stepwise palladium and silver precipitation, electrolyte replenishment and purification, and gold recovery. It completely eliminates chlorine-containing reagents and avoids the generation of gold-separating sludge, solving the problems of difficult gold-separating sludge washing, large process footprint, and low gold and silver recovery rates in traditional processes. It also eliminates the corrosion of equipment, furnace bricks, and flues by chlorine-containing reagents, extending equipment lifespan and reducing maintenance costs. Furthermore, it eliminates the need for pyrometallurgical remelting, reducing hazardous waste generation and treatment costs. By optimizing the selection of leaching agents, palladium precipitation reagents, and silver precipitation reagents, and process parameters, a silver leaching rate of ≥98%, a palladium recovery rate of ≥99%, and a high-quality gold ingot rate of ≥99.5% are achieved. Silver can be replenished in situ to the electrolyte without additional electrolyte preparation. The silver precipitation solution can be purified and recycled as a leaching agent, reducing reagent and pure water consumption and wastewater discharge. This process balances high-efficiency recovery, environmental friendliness, and cost control, and is simple, controllable, and suitable for large-scale industrial production. Attached Figure Description

[0019] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0020] Figure 1 A process flow diagram of the present invention is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Reference Appendix Figure 1 A fully wet process for treating silver anode mud without chlorine or gold-separating slag includes the following steps:

[0023] (1) Chlorine-free selective leaching: Silver anode mud is mixed with chlorine-free leaching agent at a liquid-solid ratio of 8-12:1 and leached at 75-85℃ for 3-5 hours. After filtration and separation, gold-containing leaching residue and silver-palladium-containing leaching solution are obtained. The chlorine-free leaching agent is nitric acid solution with a concentration of 2.5-3.5 mol / L.

[0024] (2) Stepwise palladium precipitation: Add palladium precipitation reagent to the silver-palladium leaching solution obtained in step (1), adjust the pH value to 1.5-2.5, react at 55-65℃ for 1.5-2.5h, filter to obtain palladium precipitate and palladium precipitation solution; the palladium precipitation reagent is dimethylglyoxime, and the molar ratio of the amount of palladium precipitation reagent added to palladium in the silver-palladium leaching solution is 1.2-1.5:1;

[0025] (3) Chlorine-free silver precipitation: Add silver precipitation reagent to the palladium precipitation solution obtained in step (2), adjust the pH value to 2-3, react at 40-50℃ for 1-2 hours to reduce the silver ions in the solution to silver elemental precipitate, filter to obtain silver precipitate and silver precipitation solution; the silver precipitation reagent is sodium bisulfite, and the molar ratio of the amount of silver precipitation reagent added to the silver in the palladium precipitation solution is 1.1-1.3:1;

[0026] (4) Electrolyte replenishment and purification: After dissolving the silver precipitate obtained in step (3), add it to the silver electrolysis system to replenish the electrolyte silver ions; at the same time, purify the silver precipitation liquid obtained in step (3), remove impurity ions, and return it to step (1) as a leaching agent for recycling.

[0027] (5) Gold recovery: The gold-containing leaching residue obtained in step (1) is subjected to gold separation treatment to obtain high-purity gold products.

[0028] In one embodiment of the present invention, in step (1), the silver anode mud is pretreated before leaching. The pretreatment includes crushing and grinding to make the particle size of the silver anode mud ≤100 mesh. After grinding, it is dried at 105-110℃ for 2-3 hours.

[0029] In one embodiment of the present invention, in step (2), the palladium precipitate is washed and dried, and then calcined at 700-800°C for 2-3 hours to obtain crude palladium powder. After refining the crude palladium powder, a palladium product with a purity of ≥99.95% is obtained.

[0030] In one embodiment of the present invention, in step (3), the silver precipitate is washed and then dissolved in nitric acid to obtain a silver nitrate solution. After the silver nitrate solution is filtered to remove insoluble impurities, it is directly added to the silver electrolysis system.

[0031] In one embodiment of the present invention, step (4) includes the purification treatment of the silver precipitation solution, which includes adding chelating resin to the silver precipitation solution, adjusting the pH value to 4.5-5.5, and reacting at 55-65°C and stirring at a rate of 150-200 r / min for 1-1.5 h; the amount of chelating resin added is 5%-8% of the volume of the silver precipitation solution.

[0032] Example 1

[0033] A fully wet process for treating silver anode slime without chlorine or gold-separating slag includes the following steps:

[0034] (1) Chlorine-free selective leaching: Silver anode mud raw material (composition: Cu 0.1785%, Au 58.65%, Ag 36.69%, Pd 0.9680%, Se 4.1230%, Te 0.3905%) was crushed and ground to a particle size ≤100 mesh, and dried at 105℃ for 2h to remove moisture and volatile impurities. The pretreated silver anode mud was mixed with 2.5mol / L nitric acid solution at a liquid-solid ratio of 8:1 and placed in a reaction apparatus. It was leached at a constant temperature of 75℃ for 3h with continuous stirring during the leaching process. After leaching, it was filtered to obtain gold-containing leaching residue and silver-palladium-containing leaching solution. The gold content in the leaching residue was 97.2%, the silver leaching rate was 98.5%, and the palladium leaching rate was 98.3%.

[0035] (2) Stepwise palladium precipitation: Dimethylglyoxime was added to the silver-palladium leaching solution, with a molar ratio of dimethylglyoxime to palladium in the leaching solution of 1.2:1. The pH of the solution was adjusted to 1.5, and the reaction was carried out at 55°C for 1.5 h. After the reaction was completed, the solution was filtered, and the palladium precipitate and the palladium precipitation solution were collected. The palladium precipitate was washed, dried, and calcined at 700°C for 2 h to obtain crude palladium powder. After refining, a palladium product with a purity of 99.96% was obtained, and the palladium recovery rate was 99.2%.

[0036] (3) Chlorine-free silver precipitation: Sodium bisulfite was added to the palladium precipitation solution, with a molar ratio of sodium bisulfite to silver in the palladium precipitation solution of 1.1:1. The pH of the solution was adjusted to 2, and the reaction was carried out at 40℃ for 1 h to reduce silver ions to elemental silver precipitate. After filtration, silver precipitate and silver precipitation solution were obtained. After washing, the silver precipitate was dissolved in nitric acid to obtain silver nitrate solution, and insoluble impurities were removed by filtration.

[0037] (4) Electrolyte replenishment and purification: The purified silver nitrate solution is directly added to the silver electrolysis system to replenish the silver ions in the electrolyte; chelating resin is added to the silver-precipitated liquid at a volume of 5% of the liquid volume after silver precipitation, the pH of the solution is adjusted to 4.5, and the reaction is carried out at 55℃ and a stirring rate of 150r / min for 1h. After removing impurity ions, the copper ion concentration in the purified solution is 0.08g / L, and it is returned to step (2) for recycling as a leaching agent.

[0038] (5) Gold recovery: The gold-containing leaching residue obtained in step (2) is subjected to conventional gold separation treatment to finally obtain high-purity gold products with a gold product quality rate of 99.6%.

[0039] Example 2

[0040] A fully wet process for treating silver anode slime without chlorine or gold-separating slag includes the following steps:

[0041] (1) Chlorine-free selective leaching: Silver anode mud raw material (composition: Cu 0.2926%, Au 84.43%, Ag 19.44%, Pd 1.0710%, Pt 0.3239%) was crushed and ground to a particle size ≤100 mesh, and dried at 110℃ for 3h to remove moisture and volatile impurities. The pretreated silver anode mud was mixed with 3.5mol / L nitric acid solution at a liquid-solid ratio of 12:1 and placed in a reaction apparatus. It was leached at a constant temperature of 85℃ for 5h with continuous stirring during the leaching process. After leaching, it was filtered to obtain gold-containing leaching residue and silver-palladium-containing leaching solution. The silver leaching rate was 98.2%, the palladium leaching rate was 98.1%, and the gold content in the leaching residue was 97.5%.

[0042] (2) Stepwise palladium precipitation: Dimethylglyoxime was added to the silver-palladium leaching solution, with a molar ratio of dimethylglyoxime to palladium in the leaching solution of 1.5:1. The pH of the solution was adjusted to 2.5, and the reaction was carried out at 65°C for 2.5 h. After the reaction was completed, the solution was filtered, and the palladium precipitate and the palladium precipitation solution were collected. The palladium precipitate was washed, dried, and calcined at 800°C for 3 h to obtain crude palladium powder. After refining, a palladium product with a purity of 99.97% was obtained, and the palladium recovery rate was 99.3%.

[0043] (3) Chlorine-free silver precipitation: Sodium bisulfite was added to the palladium precipitation solution, with a molar ratio of sodium bisulfite to silver in the palladium precipitation solution of 1.3:1. The pH of the solution was adjusted to 3, and the reaction was carried out at 50℃ for 2 hours to reduce silver ions to elemental silver precipitate. After filtration, silver precipitate and silver precipitation solution were obtained. After washing, the silver precipitate was dissolved in nitric acid to obtain silver nitrate solution, and insoluble impurities were removed by filtration.

[0044] (4) Electrolyte replenishment and purification: The purified silver nitrate solution is directly added to the silver electrolysis system to replenish the silver ions in the electrolyte; chelating resin is added to the silver-precipitated liquid at 8% of the volume of the silver-precipitated liquid, the pH of the solution is adjusted to 5.5, and the reaction is carried out at 65℃ and a stirring rate of 200r / min for 1.5h. After removing impurity ions, the copper ion concentration of the purified solution is 0.06g / L, and it is returned to step (2) as a leaching agent for recycling.

[0045] (5) Gold recovery: The gold-containing leaching residue obtained in step (2) is subjected to conventional gold separation treatment to finally obtain high-purity gold products with a gold product quality rate of 99.7%.

[0046] This invention provides a chlorine-free and gold-separating sludge-free wet process for treating silver anode mud. The process involves chlorine-free selective leaching, stepwise palladium and silver precipitation, electrolyte replenishment and purification, and gold recovery. It completely eliminates chlorine-containing reagents and avoids the generation of gold-separating sludge, solving the problems of difficult gold-separating sludge washing, large process footprint, and low gold and silver recovery rates in traditional processes. It also eliminates the corrosion of equipment, furnace bricks, and flues by chlorine-containing reagents, extending equipment lifespan and reducing maintenance costs. Furthermore, it eliminates the need for pyrometallurgical remelting, reducing hazardous waste generation and treatment costs. By optimizing the selection of leaching agents, palladium precipitation reagents, and silver precipitation reagents, and process parameters, a silver leaching rate of ≥98%, a palladium recovery rate of ≥99%, and a high-quality gold ingot rate of ≥99.5% are achieved. Silver can be replenished in situ to the electrolyte without additional electrolyte preparation. The silver precipitation solution can be purified and recycled as a leaching agent, reducing reagent and pure water consumption and wastewater discharge. This process balances high-efficiency recovery, environmental friendliness, and cost control, and is simple, controllable, and suitable for large-scale industrial production.

[0047] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A fully wet process for treating silver anode mud without chlorine or gold-separating slag, characterized in that, Includes the following steps: (1) Chlorine-free selective leaching: Silver anode mud is mixed with chlorine-free leaching agent at a liquid-solid ratio of 8-12:1 and leached at 75-85℃ for 3-5 hours. After filtration and separation, gold-containing leaching residue and silver-palladium-containing leaching solution are obtained. The chlorine-free leaching agent is a nitric acid solution with a concentration of 2.5-3.5 mol / L. (2) Stepwise palladium precipitation: Add palladium precipitation reagent to the silver-palladium leaching solution obtained in step (1), adjust the pH value to 1.5-2.5, react at 55-65℃ for 1.5-2.5h, filter to obtain palladium precipitate and palladium precipitation solution; the palladium precipitation reagent is dimethylglyoxime, and the molar ratio of the amount of palladium precipitation reagent added to palladium in the silver-palladium leaching solution is 1.2-1.5:1; (3) Chlorine-free silver precipitation: Add silver precipitation reagent to the palladium precipitation solution obtained in step (2), adjust the pH value to 2-3, react at 40-50℃ for 1-2 hours to reduce the silver ions in the solution to silver elemental precipitate, filter to obtain silver precipitate and silver precipitation solution; the silver precipitation reagent is sodium bisulfite, and the molar ratio of the amount of silver precipitation reagent added to the silver in the palladium precipitation solution is 1.1-1.3:1; (4) Electrolyte replenishment and purification: After dissolving the silver precipitate obtained in step (3), add it to the silver electrolysis system to replenish the electrolyte silver ions; at the same time, purify the silver precipitation liquid obtained in step (3), remove impurity ions, and return it to step (1) as a leaching agent for recycling. (5) Gold recovery: The gold-containing leaching residue obtained in step (1) is subjected to gold separation treatment to obtain high-purity gold products.

2. The fully wet process for treating silver anode mud without chlorine or gold-separating slag as described in claim 1, characterized in that, In step (1), the silver anode mud is pretreated before leaching. The pretreatment includes crushing and grinding to make the particle size of the silver anode mud ≤100 mesh. After grinding, it is dried at 105-110℃ for 2-3 hours.

3. The fully wet process for treating silver anode mud without chlorine or gold-separating slag as described in claim 1, characterized in that, In step (2), the palladium precipitate is washed, dried, and then calcined at 700-800℃ for 2-3 hours to obtain crude palladium powder. The crude palladium powder is then refined to obtain a palladium product with a purity of ≥99.95%.

4. The fully wet process for treating silver anode mud without chlorine or gold-separating slag as described in claim 1, characterized in that, In step (3), the silver precipitate is washed and then dissolved in nitric acid to obtain a silver nitrate solution. After filtering to remove insoluble impurities, the silver nitrate solution is directly added to the silver electrolysis system.

5. The fully wet process for treating silver anode mud without chlorine or gold-separating slag as described in claim 1, characterized in that, In step (4), the purification treatment of the silver precipitation solution includes: adding chelating resin to the silver precipitation solution, adjusting the pH value to 4.5-5.5, and reacting at 55-65℃ and stirring rate of 150-200r / min for 1-1.5h; the amount of chelating resin added is 5%-8% of the volume of the silver precipitation solution.

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