A method for enriching precious metals from high-sulfur materials

Abstract

The present invention provides a method for enriching precious metals from high-sulfur materials. The material's main components are: ∑Pt+Pd+Au 0.2%-0.25%, Ni 30%-40%, Cu 15%-20%, and S 15%-25%. The enrichment method, which includes chlorination leaching, oxidative modification, microwave drying, and vacuum distillation, can separate and recover elemental sulfur from the high-sulfur material and efficiently enrich precious metals. The resulting sulfur purity can reach over 95%, with a sulfur removal rate exceeding 95%. The precious metal (platinum, palladium, and gold) concentration is enriched from 2000-2500 g / t to approximately 8-12%, an enrichment multiple of over 30 times, demonstrating significant results.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for enriching precious metals from high-sulfur materials. Background Art

[0002] The main methods for enriching precious metals from PGM high-nickel matte (sulfur-containing PGM materials) include atmospheric pressure acid leaching, controlled potential chloride leaching, pressure leaching, and roasting leaching. Atmospheric pressure acid leaching utilizes the ability of hydrochloric acid, sulfuric acid, and nitric acid to react with various metals, metal oxides, and certain metal sulfides to form soluble chlorides, sulfates, or nitrates that enter the solution. Precious metals, remaining insoluble, are concentrated in the leached residue. Chloride leaching is a wet chlorination process conducted in an aqueous medium, whereby valuable metals in the raw material are dissolved as chlorides. Pressure leaching is an effective means of intensifying the leaching process and a highly efficient technique for separating precious and base metals. In a sealed vessel, the system temperature is raised to above the atmospheric boiling point of the leaching medium, and high-pressure air or oxygen is introduced to oxidize base metals such as Ni, Fe, Co, and Cu, or their sulfides, into soluble sulfates, which are then separated from the precious metals remaining in the leached residue.

[0003] With the increasing scarcity of platinum group metal (PGM) mineral resources, enriching PGMs from secondary sources or metal smelting waste slags is becoming increasingly important. This is particularly true for smelting intermediate slags, which are high in sulfur and contain a mixture of metals and sulfides. These intermediate slags primarily consist of ∑Pt + Pd + Au 0.2%-0.25%, Ni 30%-40%, Cu 15%-20%, S 15%-25%, and the remainder is other impurities. Existing processes are difficult to fully remove nickel, copper, and sulfur, necessitating the development of a process suitable for this material to recover precious metals and improve resource utilization. Summary of the Invention

[0004] In response to the problems existing in the above background technology, the present invention discloses a method for enriching precious metals from high-sulfur materials. The method can separate and recover elemental sulfur from high-sulfur materials and efficiently enrich precious metals.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for enriching precious metals from high-sulfur materials comprises the following steps:

[0007] 1) The high-sulfur material and water are slurried at a solid-liquid ratio of 1:5-7, and hydrochloric acid is added to adjust the hydrogen ion concentration to 2.0-2.5 mol / L. The mixture is placed in a reaction vessel and stirred thoroughly. The temperature is raised to 80-85°C, and chlorine gas is then introduced to gradually increase the system potential to 390-410 mV. Once the potential reaches the required potential, the reaction is stopped and the solid-liquid separation is performed to obtain a filter residue and a filtrate. The filtrate is sent to a nickel plant to recover nickel and copper, and the filter residue is sent to the next step for treatment.

[0008] 2) The filter residue obtained after chlorination leaching in step 1) is slurried at a solid-liquid ratio of 1:3-4, hydrochloric acid is added to adjust the hydrogen ion concentration to 2.5-3.5 mol / L, the temperature is raised to 80-85°C, chlorine gas is continuously introduced, the system potential is adjusted to 380-385 mV, and the potential is maintained constant for 8-12 hours, followed by solid-liquid separation to obtain a filtrate and a filter residue. The filtrate is returned to step 1) for reuse, and the filter residue is sent to the next step for treatment;

[0009] 3) subjecting the filter residue obtained in step 2) to microwave drying to control the moisture content of the residue to less than 3%, thereby obtaining dried oxidatively modified residue;

[0010] 4) The dried oxidized modified slag obtained in step 3) is placed in a vacuum distillation furnace and subjected to vacuum distillation at a vacuum degree of 50 to 600 Pa at a temperature of 200 to 300° C. for 4 to 8 hours to produce sulfur- and precious metal-enriched slag.

[0011] In steps 1-4 above, the high-sulfur material primarily comprises: ∑Pt + Pd + Au 0.2%-0.25%, Ni 30%-40%, Cu 15%-20%, S 15%-25%, with the remainder being other impurity elements. The vacuum is preferably 50-200 Pa. The temperature is preferably 200-240°C. The reaction time is preferably 4-5 hours.

[0012] The sulfur slag obtained in step (4) can be sold externally, and the precious metal enriched slag can be returned to the platinum group metal production process to extract precious metals such as gold, platinum, and palladium.

[0013] Reaction mechanism of the present invention:

[0014] In the hydrochloric acid medium, by controlling the amount of chlorine gas introduced, the solution is kept at a certain oxidation potential, so that the base metal undergoes oxidation reaction and enters the solution, while the precious metal does not react and remains in the slag, thereby achieving the purpose of separating the precious and base metals. Wherein the metal element nickel and copper have high reaction activity and fast reaction rate. They can be leached in large quantities in the control electrochlorination stage, resulting in a large increase in nickel and copper ions in the solution, while the reaction rate of sulfides such as copper sulfide and nickel sulfide is not as fast as metal element nickel and copper. When the nickel and copper ion content in the solution is high, the reaction of copper sulfide and nickel sulfide to generate elemental sulfur will not be thorough, making the nickel and copper content in the leached slag higher, affecting subsequent vacuum desulfurization, and reducing the desulfurization rate. Therefore, after the solution and slag of the control electrochlorination process are carried out solid-liquid separation, oxidation leaching is further carried out, and the remaining copper sulfide and nickel sulfide are thoroughly oxidized to generate copper chloride, nickel chloride and elemental sulfur, which is convenient for the next step of desulfurization treatment.

[0015] The main reaction formula is as follows:

[0016] Ni+2HCl=NiCl2+H2↑

[0017] Ni + Cl2 = NiCl2

[0018] Cu + Cl2 = CuCl2

[0019] Ni+2CuCl2= NiCl2+2CuCl

[0020] 2CuCl + Cl2 = 2CuCl2

[0021] CuS+Cl2= CuCl2+S↓

[0022] NiS+Cl2= NiCl2+S↓

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The method of the present invention, through chlorination leaching, oxidation modification, microwave drying, and vacuum distillation, can separate and recover elemental sulfur from high-sulfur materials and efficiently enrich precious metals. The resulting sulfur purity can reach over 95%, with a sulfur removal rate exceeding 95%. The precious metal (platinum, palladium, and gold) concentration is increased from 2000-2500 g / t to approximately 8-12%, an enrichment multiple of over 30 times, demonstrating significant results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to specific embodiments. Figure 1, the present invention is further described in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0027] Example 1

[0028] Raw material 1 consists of ∑Pt + Pd + Au 0.21%, Ni 33%, Cu 15%, and S 15%. Hydrochloric acid is added to a solid-liquid ratio of 1:5, and the hydrogen ion concentration is adjusted to 2.0 mol / L. The mixture is then placed in a reaction vessel and stirred thoroughly. The temperature is raised to 80°C, and chlorine gas is introduced to raise the potential to 390 mV. Once the potential reaches the desired level, the reaction is stopped, the reaction is discharged, and the residue is filtered to obtain a residue. The residue is slurried at a solid-liquid ratio of 1:3, and hydrochloric acid is added to adjust the hydrogen ion concentration to 2.5 mol / L. The temperature is raised to 80°C, and the system potential is adjusted to 380 mV. The potential is maintained constant for 8 hours, and the system is separated into solid and liquid to obtain a residue. The residue is microwave-dried and placed in a vacuum distillation furnace for vacuum distillation at 50-100 Pa at 200°C for 4 hours. The resulting residue is sulfur- and precious metal-enriched. The sulfur content is 96.25%, the raw material desulfurization rate is 96.3%, and the precious metal enrichment is 32 times.

[0029] Example 2

[0030] Raw material 2 consists of ∑Pt + Pd + Au 0.23%, Ni 35%, Cu 18%, and S 17%. Hydrochloric acid is added to a solid-liquid ratio of 1:6, and the hydrogen ion concentration is adjusted to 2.0 mol / L. The mixture is then placed in a reaction vessel and stirred thoroughly. The temperature is raised to 85°C, and chlorine gas is introduced to raise the potential to 400 mV. Once the potential reaches the desired level, the reaction is stopped, the materials are discharged, and the residue is filtered. The residue is slurried at a solid-liquid ratio of 1:4, and hydrochloric acid is added to adjust the hydrogen ion concentration to 2.5 mol / L. The temperature is raised to 85°C, and the system potential is adjusted to 385 mV. The potential is maintained constant for 10 hours, and the system is separated into solid and liquid to obtain the residue. The residue is microwave-dried and placed in a vacuum distillation furnace for vacuum distillation at a temperature of 250°C for 5 hours at a vacuum of 100-150 Pa. The resulting residue is sulfur- and precious metal-enriched. The sulfur content is 97.85%, the desulfurization rate is 97.4%, and the precious metal enrichment is 33 times.

[0031] Example 3

[0032] The raw materials consist of ∑Pt + Pd + Au 0.25%, Ni 40%, Cu 20%, and S 25%. Hydrochloric acid was added to adjust the hydrogen ion concentration to 2.5 mol / L at a solid-to-liquid ratio of 1:7. The mixture was placed in a reaction vessel and stirred thoroughly. The temperature was raised to 85°C, and chlorine gas was introduced to raise the potential to 410 mV. Once the potential reached the desired level, the reaction was stopped, the materials were discharged, and the residue was filtered. The residue was slurried at a solid-to-liquid ratio of 1:4, hydrochloric acid was added to adjust the hydrogen ion concentration to 3.5 mol / L, and the temperature was raised to 85°C. The system potential was adjusted to 385 mV and the potential was maintained constant for 12 hours. The solid-liquid separation was then performed to obtain the residue. The residue was microwave-dried and placed in a vacuum distillation furnace for vacuum distillation at 200 Pa at 240°C for 5 hours. The resulting residue contained sulfur and precious metals, with a sulfur content of 98.15%, a desulfurization rate of 98.4%, and a precious metal enrichment of 34 times.

Claims

1. A method for enriching precious metals from high-sulfur materials, characterized in that: The following steps are involved: 1) The high-sulfur material and water are slurried at a solid-liquid ratio of 1:5-7, and hydrochloric acid is added to adjust the hydrogen ion concentration to 2.0-2.5 mol / L. The mixture is placed in a reaction vessel and stirred thoroughly. The temperature is raised to 80-85°C, and chlorine gas is then introduced to gradually increase the system potential to 390-410 mV. Once the potential reaches the required potential, the reaction is stopped and the solid-liquid separation is performed to obtain a filter residue and a filtrate. The filtrate is sent to a nickel plant to recover nickel and copper, and the filter residue is sent to the next step for treatment. 2) The filter residue obtained after chlorination leaching in step 1) is slurried at a solid-liquid ratio of 1:3-4, hydrochloric acid is added to adjust the hydrogen ion concentration to 2.5-3.5 mol / L, the temperature is raised to 80-85°C, chlorine gas is continuously introduced, the system potential is adjusted to 380-385 mV, and the potential is maintained constant for 8-12 hours, followed by solid-liquid separation to obtain a filtrate and a filter residue. The filtrate is returned to step 1) for reuse, and the filter residue is sent to the next step for treatment; 3) subjecting the filter residue obtained in step 2) to microwave drying to control the moisture content of the residue to less than 3%, thereby obtaining dried oxidatively modified residue; 4) placing the dried oxidized modified slag obtained in step 3) in a vacuum distillation furnace and performing vacuum distillation at a vacuum degree of 50-200 Pa at a temperature of 200-240° C. for 4-5 hours to produce sulfur- and precious metal-enriched slag.

2. A method for enriching precious metals from high-sulfur materials according to claim 1, characterized in that: The main components of the high-sulfur material are: ∑Pt+Pd+Au 0.2%~0.25%, Ni 30%~40%, Cu 15%~20%, S 15%~25%, and the rest are other impurity elements.

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