A method for extracting silver from refractory silver-containing rhodochrosite

Abstract

The present invention proposes a method for extracting silver from refractory silver-bearing rhodochrosite ore, comprising the following steps: crushing and finely grinding the silver-bearing rhodochrosite ore, followed by mineral phase reconstitution with an acid and a chloride additive to obtain slurry 1; subjecting slurry 1 to solid-liquid separation to obtain a filtrate and a residue; subjecting the residue to a leaching reaction with a lixiviant to obtain slurry 2; subjecting slurry 2 to solid-liquid separation to obtain a silver-containing leachate and a leaching residue; and adding a reducing agent to the silver-containing leachate to carry out a displacement reaction to obtain a silver concentrate containing metallic silver. The present invention utilizes mineral phase reconstitution to disrupt the crystal structure of the iron-manganese carbonate mineral, exposing the encapsulated silver, increasing the contact area with the lixiviant, promoting ion diffusion, and ultimately achieving efficient silver leaching, significantly improving the silver leaching rate.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral processing, and in particular to a method for extracting silver from refractory silver-containing rhodochrosite. Background Art

[0002] Silver exists in nature in small amounts as elemental silver, but in larger amounts as compounds associated with other metallic minerals. Among sulfide ores, silver is most commonly found in galena, chalcopyrite, and sphalerite.

[0003] Silver ore beneficiation primarily involves gravity separation and flotation. Independent silver mines in China primarily producing silver generally employ flotation, while co-existing silver mines often employ a combination of flotation, flotation-gravity separation, and flotation-cyanidation processes, with flotation being the most important. Silver is extracted primarily through hydrometallurgy and pyrometallurgy. Silver ores associated with lead, zinc, and copper are typically separated based on the process conditions and reagent systems of the primary metals. Silver is typically concentrated in lead, zinc, and copper concentrates and then recovered through smelting. Silver is recovered from the beneficiation products of some independent silver mines and co-existing gold and silver ores through hydrocyanidation, while some low-grade silver mines utilize heap leaching.

[0004] A silver-bearing rhodochrosite ore, whose mineral composition mainly consists of rhodochrosite (siderite), magnetite, quartz, ankerite, garnet, etc., contains 60-120g / t of Ag. The silver minerals are mainly fine-grained and embedded in iron-manganese carbonate minerals and quartz and other minerals. The silver minerals are fine and encapsulated. Flotation-leaching, grinding-leaching, ultrafine grinding-leaching, ultrafine grinding-flotation-leaching and other processes have been used on the silver-bearing rhodochrosite ore, but the Ag leaching rate does not exceed 5%, and ideal technical indicators have not been achieved.

[0005] Patent document CN103773971B discloses a method for improving the silver leaching rate of a polymetallic gold concentrate using a roasting-acid leaching-cyanidation process. The polymetallic gold concentrate is mixed with sodium hydroxide, roasted, and acid-leached to produce an acid leaching residue. The acid leaching residue is then exposed to an acidic fluoride salt system to enhance mineral phase reconstruction, followed by cyanide leaching. While roasting in this method does help improve the silver leaching rate, the Ag leaching rate is still around 40%. Summary of the Invention

[0006] The present invention provides a method for extracting silver from refractory silver-containing rhodochrosite, aiming to solve the problem of efficient separation and recycling of silver in the silver-containing rhodochrosite.

[0007] The technical solution of the present invention is achieved as follows: a method for extracting silver from refractory silver-containing rhodochrosite, comprising the following steps:

[0008] (1) crushing and fine-grinding the silver-containing ferromanganese ore to obtain fine-grained minerals;

[0009] (2) Mineral phase reconstruction: fine-grained minerals are stirred and reacted with acid and chloride additive to obtain slurry 1;

[0010] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed to obtain a filtrate and a residue;

[0011] (4) Leaching of silver: The residue is subjected to a leaching reaction with a leaching agent to obtain slurry 2.

[0012] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed to obtain a silver-containing leachate and leach residue;

[0013] (6) Silver precipitation: A reducing agent is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver.

[0014] Furthermore, in step (1), the fine grinding to -0.045 mm accounts for 60%-95%.

[0015] Furthermore, in step (2), the acid is sulfuric acid or hydrochloric acid, and the amount is 0.5-3 mol / L; the auxiliary agent is NaCl, and the amount is 0-2 mol / L; the reaction conditions are: liquid-solid ratio 2:1-6:1, temperature 5°C-40°C, and time 0.5-8h.

[0016] Furthermore, in step (4), lime is used to control the pH of the reaction solution to 11-12.5; the leaching agent is sodium cyanide, and the dosage is 0.5-8 mol / L; the reaction conditions are: liquid-solid ratio 3:1-6:1, temperature 10°C-40°C, and time 12-72h.

[0017] Furthermore, in step (6), the reducing agent is zinc powder, and the amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.5-0.6:1.

[0018] The principle of the present invention is:

[0019] (1) Mineral phase reconstruction: The rhodochrosite in the ore reacts chemically with the acid to destroy the crystal structure of the silver-containing iron-manganese carbonate mineral, thereby fully exposing the encapsulated silver, increasing the contact area between the leaching agent and the silver in the subsequent silver leaching operation, and achieving efficient cyanide leaching of silver. The chemical reaction that occurs is shown in formula (1).

[0020] MnFe(CO3)2+ 2H2SO4=MnSO4+ FeSO4+ 2CO2↑+ 2H2O (1)

[0021] The ore also contains a small amount of magnetite, ankerite, garnet and other minerals. The following reactions may occur during the mineral phase reconstruction process:

[0022] Fe3O4+ 4H2SO4=FeSO4+ Fe2(SO4)3+ 4H2O (2)

[0023] CaCO3+ H2SO4=CaSO4+ CO2↑+H2O (3)

[0024] MgCO3+ H2SO4=MgSO4+ CO2↑+H2O (4)

[0025] FeCO3+ H2SO4=FeSO4+ CO2↑+H2O (5)

[0026] Additive Cl - (NaCl) role: In the sulfuric acid reaction system, Cl - Through the chemical reaction of hydrochloric acid, calcium carbonate is consumed and the solubility of calcium sulfate is increased, thereby reducing the thickness of the CaSO4 coating layer on the mineral surface, while increasing the specific surface area and pore volume of the leaching residue, destroying the structure of the rhodochrosite mineral, promoting ion diffusion, and ultimately promoting the leaching of silver.

[0027] (2) Silver leaching: The exposed silver reacts chemically with sodium cyanide and enters the solution. The chemical reactions are shown in formulas (6) and (7).

[0028] 2Ag+ 4NaCN+ O2 + 2H2O=2NaAg(CN)2+ 2NaOH+ H2O2 (6)

[0029] 2Ag+ 2NaCN+ H2O2=2NaAg(CN)2+ 2NaOH (7)

[0030] (3) Silver precipitation: Zinc powder reacts chemically with the silver leaching solution to obtain silver concentrate containing metallic silver. The chemical reaction is shown in formula (8).

[0031] 2Ag + + Zn=2Ag↓+ Zn 2+ (8)

[0032] Beneficial effects of the present invention:

[0033] The present invention destroys the crystal structure of the iron-manganese carbonate mineral through mineral phase reconstruction, exposing silver distributed in isomorphous form within the iron-manganese carbonate mineral lattice and silver distributed as fine-grained inclusions within the iron-manganese carbonate mineral or in microcracks. This increases the contact area between the leaching agent and the silver, improves the specific surface area and pore volume of the leached residue, promotes ion diffusion, and ultimately achieves efficient cyanide leaching of silver, significantly increasing the cyanide leaching rate of silver. Tests have shown that the direct cyanide leaching rate of silver in silver-containing rhodochrosite is 2-5%, making it a typical difficult-to-smelt silver ore and difficult to develop economically. However, the present invention, by first reconstructing the mineral phase and then cyaniding, can ultimately increase the silver leaching rate to over 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 The present invention provides a flow chart of a method for extracting silver from refractory silver-containing rhodochrosite. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, a method for extracting silver from refractory silver-containing rhodochrosite comprises the following steps:

[0039] (1) Sample preparation: The ore containing 60.53 g / t of Ag was crushed and finely ground to obtain fine-grained minerals with a particle size of -0.045 mm accounting for 60%;

[0040] (2) Mineral phase reconstruction: fine-grained minerals were reacted with 0.5 mol / L sulfuric acid at a liquid-to-solid ratio of 2:1 and a temperature of 5°C for 0.5 h to obtain slurry 1;

[0041] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed 2-3 times to obtain a filtrate and a residue;

[0042] (4) Silver leaching: The residue was pretreated with lime, the pH of the solution was controlled to 11, 0.5 mol / L sodium cyanide was added, and the reaction was carried out at a liquid-solid ratio of 3:1 and a temperature of 10°C for 12 hours to obtain slurry 2.

[0043] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed 2-3 times to obtain a silver-containing leachate and leach residue;

[0044] (6) Silver precipitation: zinc powder is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver. The amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.6:1.

[0045] The final Ag leaching rate obtained from the experiment was 80.59%.

[0046] Example 2:

[0047] like Figure 1 As shown, a method for extracting silver from refractory silver-containing rhodochrosite comprises the following steps:

[0048] (1) Sample preparation: The ore containing 65.85 g / t of Ag was crushed and finely ground to obtain fine-grained minerals with a particle size of -0.045 mm accounting for 85%;

[0049] (2) Mineral phase reconstruction: fine-grained minerals were reacted with 2 mol / L sulfuric acid and 1 mol / L NaCl at a liquid-solid ratio of 4:1 and a temperature of 25°C for 4 h to obtain slurry 1;

[0050] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed 2-3 times to obtain a filtrate and a residue;

[0051] (4) Silver leaching: The residue was pretreated with lime, the pH of the solution was controlled to 11.5, 3 mol / L sodium cyanide was added, and the reaction was carried out at a liquid-to-solid ratio of 4:1 and a temperature of 25°C for 48 hours to obtain slurry 2.

[0052] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed 2-3 times to obtain a silver-containing leachate and leach residue;

[0053] (6) Silver precipitation: zinc powder is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver. The amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.6:1.

[0054] The final Ag leaching rate obtained from the experiment was 88.72%.

[0055] Example 3:

[0056] like Figure 1 As shown, a method for extracting silver from refractory silver-containing rhodochrosite comprises the following steps:

[0057] (1) Sample preparation: The ore containing 90.20 g / t of Ag was crushed and finely ground to obtain fine-grained minerals with a particle size of -0.045 mm accounting for 95%;

[0058] (2) Mineral phase reconstruction: fine-grained minerals were reacted with 3 mol / L sulfuric acid and 2 mol / L NaCl at a liquid-solid ratio of 6:1 and a temperature of 40°C for 8 h to obtain slurry 1;

[0059] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed 2-3 times to obtain a filtrate and a residue;

[0060] (4) Silver leaching: The residue was pretreated with lime, the pH of the solution was controlled to 12.5, 8 mol / L sodium cyanide was added, and the reaction was carried out at a liquid-to-solid ratio of 6:1 and a temperature of 10°C for 72 hours to obtain slurry 2.

[0061] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed 2-3 times to obtain a silver-containing leachate and leach residue;

[0062] (6) Silver precipitation: zinc powder is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver. The amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.55:1.

[0063] The final Ag leaching rate obtained from the experiment was 93.57%.

[0064] Example 4:

[0065] like Figure 1 As shown, a method for extracting silver from refractory silver-containing rhodochrosite comprises the following steps:

[0066] (1) Sample preparation: Ore containing 120 g / t of Ag was crushed and finely ground to obtain fine-grained minerals with a particle size of -0.045 mm accounting for 90%;

[0067] (2) Mineral phase reconstruction: fine-grained minerals were reacted with 2.5 mol / L sulfuric acid and 1.5 mol / L NaCl at a liquid-solid ratio of 5:1 and a temperature of 35°C for 6 h to obtain slurry 1;

[0068] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed 2-3 times to obtain a filtrate and a residue;

[0069] (4) Silver leaching: The residue was pretreated with lime, the pH of the solution was controlled to 12, 6 mol / L sodium cyanide was added, and the reaction was carried out at a liquid-to-solid ratio of 5:1 and a temperature of 35°C for 48 hours to obtain slurry 2.

[0070] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed 2-3 times to obtain a silver-containing leachate and leach residue;

[0071] (6) Silver precipitation: zinc powder is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver. The amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.55:1.

[0072] The final Ag leaching rate obtained from the experiment was 92.34%.

[0073] Example 5:

[0074] like Figure 1 As shown, a method for extracting silver from refractory silver-containing rhodochrosite comprises the following steps:

[0075] (1) Sample preparation: The ore containing 93 g / t of Ag was crushed and finely ground to obtain fine-grained minerals with a diameter of -0.045 mm accounting for 92%;

[0076] (2) Mineral phase reconstruction: fine-grained minerals were reacted with 2 mol / L sulfuric acid and 1 mol / L NaCl at a liquid-solid ratio of 4:1 and a temperature of 30°C for 5 h to obtain slurry 1;

[0077] (3) solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed 2-3 times to obtain a filtrate and a residue;

[0078] (4) Silver leaching: The residue was pretreated with lime, the pH of the solution was controlled to 11.5, 6 mol / L sodium cyanide was added, and the reaction was carried out at a liquid-to-solid ratio of 4:1 and a temperature of 30°C for 60 h to obtain slurry 2.

[0079] (5) solid-liquid separation: slurry 2 is subjected to solid-liquid separation and washed 2-3 times to obtain a silver-containing leachate and leach residue;

[0080] (6) Silver precipitation: zinc powder is added to the silver-containing leaching solution to react and obtain a silver concentrate containing metallic silver. The amount of zinc powder used is such that the molar ratio of Zn:Ag is 0.6:1.

[0081] The final Ag leaching rate obtained from the experiment was 91.66%.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for extracting silver from refractory silver-containing rhodochrosite, characterized in that: The following steps are involved: (1) Crushing and grinding silver-containing ferromanganese ore to obtain fine-grained minerals; (2) Mineral phase reconstruction: fine-grained minerals are stirred and reacted with acid and chloride additive to obtain slurry 1; (3) Solid-liquid separation: slurry 1 is subjected to solid-liquid separation and washed to obtain a filtrate and a residue; (4) Leaching of silver: the residue is subjected to a leaching reaction with a leaching agent to obtain slurry 2; (5) Solid-liquid separation: Slurry 2 is subjected to solid-liquid separation and washing to obtain a silver-containing leachate and leach residue; (6) Silver precipitation: adding a reducing agent to the silver-containing leaching solution to carry out a replacement reaction to obtain a silver concentrate containing metallic silver; In step (1), fine grinding to -0.045mm accounts for 60%-95%; In step (2), the acid is sulfuric acid, and the amount is 0.5-3 mol / L; the chloride auxiliary agent is NaCl, and the amount is 1-2 mol / L; the reaction conditions are: liquid-solid ratio 2:1-6:1, temperature 5°C-40°C, and time 0.5-8h; In step (4), lime is used to control the pH of the reaction solution to 11-12.5; the leaching agent is sodium cyanide, and the amount used is 0.5-8 mol / L; the reaction conditions are: liquid-solid ratio 3:1-6:1, temperature 10°C-40°C, and time 12-72h; In step (6), the reducing agent is zinc powder, and the molar ratio of Zn:Ag is 0.5-0.6:1.

Images