A method for recovering precious metals from sodium thiosulfate filter press residue

Abstract

The present invention relates to a method for recovering precious metals from sodium thiosulfate filter press residues, comprising the following steps: dissolving the filter press residues with water, performing precise filtration and impurity removal, evaporating and concentrating the filtered filtrate twice, adding hydrochloric acid to adjust the pH value of the solution, and introducing chlorine gas for oxidation to obtain precious metal precipitates. The present invention realizes the recovery of Pt, Pd and Au precious metals in the sodium thiosulfate filter press residues, and the recovery rate of precious metals reaches more than 99%, which solves the long-standing problem that a large amount of sodium thiosulfate filter press residues are difficult to cash out, improves the utilization rate of precious metal resources, and reduces the waste of precious metal resources. In addition, while extracting Pt, Pd and Au precious metals, sodium thiosulfate, sodium sulfate and sodium sulfite are also recovered, which realizes the maximum utilization of resources, reduces production costs, and improves the economic benefits of enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of precious metal recovery, and in particular to a method for recovering precious metals from sodium thiosulfate filter press residues. Background Art

[0002] In the hydrometallurgical process of platinum group metals, sodium sulfite solution is usually used to desulfurize materials and flue gases. The desulfurization liquid produced by this desulfurization process contains more than 98% sodium thiosulfate, and also contains Pt, Pd and Au with a total amount not exceeding 0.002g / L. Since the content of these precious metals in the desulfurization liquid is extremely low and is interfered by other components, it is difficult to extract them. At present, most companies choose to export the desulfurization liquid to small private enterprises to extract sodium thiosulfate and recover the filter residue. Specifically, for every 10m3 of treated 3 The desulfurization liquid will produce about 1 ton of filter press residue, in which the Pt content is 2-10g / t, the Pd content is 0.6-3g / t, and the Au content is 2-4.5g / t. According to the actual production situation, the annual output of desulfurization liquid is as high as 6600m 3 , it can be calculated that the amount of precious metals that can be recovered from filter press residues is 3-11.5kg per year. Due to the scarcity and high value of platinum group metals, the recycling of precious metals in filter press residues is of great significance. However, due to the difficulty of extraction, high technical barriers and lack of suitable treatment methods, most companies have failed to effectively realize these precious metals. This not only causes a waste of resources, but also limits the improvement of corporate economic benefits and the enhancement of sustainable development capabilities. Summary of the invention

[0003] In view of the difficulty in extracting precious metal elements from desulfurization hydraulic filter residue in the above-mentioned prior art, the present invention provides a method for recovering precious metals from sodium thiosulfate filter residue, which can recover more than 99% of the precious metals in the sodium thiosulfate filter residue.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for recovering precious metals from sodium thiosulfate filter press residues comprises the following steps:

[0006] (1) adding water to dissolve the filter press residue to obtain a slurry, and then finely filtering the slurry;

[0007] (2) evaporating and concentrating the filtrate obtained in step (1) at 95-100° C. to form a saturated sodium sulfate solution, filtering the saturated sodium sulfate solution at 45-50° C., and obtaining a filter residue comprising sodium sulfate and sodium sulfite;

[0008] (3) evaporating and concentrating the filtrate obtained in step (2) at 95-100° C. to form a saturated sodium thiosulfate solution, filtering the saturated sodium thiosulfate solution at 75-80° C., and obtaining a filter residue comprising sodium thiosulfate;

[0009] (4) adding hydrochloric acid to the filtrate obtained in step (3), and continuously introducing chlorine gas to maintain the potential in the filtrate at 395±20 mV;

[0010] (5) filtering the feed liquid after the reaction in step (4) to obtain a precious metal precipitate and a filtrate, separating and purifying the precious metal precipitate to obtain the precious metal, and using the filtrate to prepare acid in the raw material treatment process.

[0011] Furthermore, in step (1), a 0.5 μm precision filter is used to filter the slurry.

[0012] Furthermore, the time for introducing chlorine gas in step (4) is 4-6 hours.

[0013] Furthermore, the concentration of the hydrochloric acid in step (4) is 15-20%.

[0014] Furthermore, in step (4), hydrochloric acid is added in a ratio of 1:8-10 to the volume of the filtrate obtained in step (3).

[0015] Furthermore, the precious metal precipitate in step (4) includes precious metal chloride.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a method for recovering precious metals from sodium thiosulfate filter press residues. First, insoluble impurities in the slurry are removed by precision filtration. Then, sodium sulfate and sodium sulfite are separated from the filtrate by two evaporation concentrations, respectively, by utilizing the large difference in solubility between sodium sulfate and sodium sulfite and sodium thiosulfate. Finally, precious metal precipitates are obtained by chlorine oxidation, thereby realizing the recovery of Pt, Pd and Au precious metals in the sodium thiosulfate filter press residues. The recovery rate of precious metals reaches more than 99%, solving the problem that a large amount of sodium thiosulfate filter press residues are difficult to cash out for a long time, improving the utilization rate of precious metal resources, reducing the waste of precious metal resources, and having important significance for promoting the sustainable development of the precious metal industry. In addition, while extracting Pt, Pd and Au precious metals, sodium thiosulfate, sodium sulfate and sodium sulfite are also recovered, thereby realizing the maximum utilization of resources, reducing production costs and improving the economic benefits of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0019] Figure 1 A process flow chart for recovering precious metals from sodium thiosulfate filter press residues is shown. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] Example 1

[0022] A method for recovering precious metals from sodium thiosulfate filter press residues comprises the following steps:

[0023] (1) adding water to dissolve the filter press residue to obtain a slurry, and filtering the slurry through a 0.5 μm precision filter;

[0024] (2) evaporating and concentrating the filtrate obtained in step (1) at 100° C. to obtain a saturated sodium sulfate solution, filtering the saturated sodium sulfate solution at 50° C., and obtaining a filter residue comprising sodium sulfate and sodium sulfite;

[0025] (3) evaporating and concentrating the filtrate obtained in step (2) at 100° C. to obtain a saturated sodium thiosulfate solution, filtering the saturated sodium thiosulfate solution at 80° C., and obtaining a filter residue comprising sodium thiosulfate;

[0026] (4) adding 20% ​​hydrochloric acid to the filtrate obtained in step (3) at a ratio of 1:10, and continuously passing chlorine gas for 6 h to maintain the potential in the filtrate at 415 mV;

[0027] (5) filtering the feed liquid after the reaction in step (4) to obtain a precious metal precipitate and a filtrate, separating and purifying the precious metal precipitate to obtain the precious metal, and using the filtrate to prepare acid in the raw material treatment process.

[0028] The separation and purification processes of precious metal precipitates include distillation, gold extraction, copper, cobalt and nickel precipitation, platinum and palladium reduction, platinum and palladium separation, and refining of platinum and palladium.

[0029] In this embodiment, the Pt content in the filter press residue is 3.5 g / t, the Pd content is 2.8 g / t, and the Au content is 3 g / t. After 500 kg of filter press residue with a water content of 12% is treated by the above method, the sum of the masses of Pt, Pd, and Au in the precious metal precipitate obtained is 4.05 g, and the precious metal yield is 99.02%.

[0030] Example 2

[0031] A method for recovering precious metals from sodium thiosulfate filter press residues comprises the following steps:

[0032] (1) adding water to dissolve the filter press residue to obtain a slurry, and filtering the slurry through a 0.5 μm precision filter;

[0033] (2) evaporating and concentrating the filtrate obtained in step (1) at 95° C. to form a saturated sodium sulfate solution, filtering the saturated sodium sulfate solution at 45° C., and obtaining a filter residue comprising sodium sulfate and sodium sulfite;

[0034] (3) evaporating and concentrating the filtrate obtained in step (2) at 95° C. to form a saturated sodium thiosulfate solution, filtering the saturated sodium thiosulfate solution at 75° C., and obtaining a filter residue comprising sodium thiosulfate;

[0035] (4) adding 15% hydrochloric acid to the filtrate obtained in step (3) at a ratio of 1:8, and continuously passing chlorine gas for 4 h to maintain the potential in the filtrate at 375 mV;

[0036] (5) filtering the feed liquid after the reaction in step (4) to obtain a precious metal precipitate and a filtrate, separating and purifying the precious metal precipitate to obtain the precious metal, and using the filtrate to prepare acid in the raw material treatment process.

[0037] The separation and purification processes of precious metal precipitates include distillation, gold extraction, copper, cobalt and nickel precipitation, platinum and palladium reduction, platinum and palladium separation, and refining of platinum and palladium.

[0038] In this embodiment, the Pt content in the filter press residue is 5.2 g / t, the Pd content is 1.8 g / t, and the Au content is 3.3 g / t. After 500 kg of the filter press residue with a water content of 8% is treated by the above method, the sum of the masses of Pt, Pd, and Au in the precious metal precipitate obtained is 4.70 g, and the precious metal yield is 99.20%.

[0039] The present invention provides a method for recovering precious metals from sodium thiosulfate filter press residues. First, insoluble impurities in the slurry are removed by precision filtration. Then, sodium sulfate and sodium sulfite are separated from the filtrate by two evaporation concentrations, respectively, by utilizing the large difference in solubility between sodium sulfate and sodium sulfite and sodium thiosulfate. Finally, precious metal precipitates are obtained by chlorine oxidation, thereby realizing the recovery of Pt, Pd and Au precious metals in the sodium thiosulfate filter press residues. The recovery rate of precious metals reaches more than 99%, solving the problem that a large amount of sodium thiosulfate filter press residues are difficult to cash out for a long time, improving the utilization rate of precious metal resources, reducing the waste of precious metal resources, and having important significance for promoting the sustainable development of the precious metal industry. In addition, while extracting Pt, Pd and Au precious metals, sodium thiosulfate, sodium sulfate and sodium sulfite are also recovered, thereby realizing the maximum utilization of resources, reducing production costs and improving the economic benefits of enterprises.

[0040] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A method for recovering precious metals from sodium thiosulfate filter press residues, characterized in that: The steps include: (1) adding water to dissolve the filter press residue to obtain a slurry, and then finely filtering the slurry; (2) evaporating and concentrating the filtrate obtained in step (1) at 95-100° C. to obtain a saturated sodium sulfate solution, filtering the saturated sodium sulfate solution at 45-50° C., and obtaining a filter residue comprising sodium sulfate and sodium sulfite; (3) evaporating and concentrating the filtrate obtained in step (2) at 95-100° C. to form a saturated sodium thiosulfate solution, filtering the saturated sodium thiosulfate solution at 75-80° C., and obtaining a filter residue comprising sodium thiosulfate; (4) adding hydrochloric acid to the filtrate obtained in step (3), and continuously introducing chlorine gas to maintain the potential in the filtrate at 395±20 mV; (5) filtering the feed liquid after the reaction in step (4) to obtain a precious metal precipitate and a filtrate, separating and purifying the precious metal precipitate to obtain the precious metal, and using the filtrate to prepare acid in the raw material treatment process.

2. A method for recovering precious metals from sodium thiosulfate filter press residue according to claim 1, characterized in that: In step (1), the slurry is filtered using a 0.5 μm precision filter.

3. A method for recovering precious metals from sodium thiosulfate filter press residue according to claim 1, characterized in that: The time for introducing chlorine in step (4) is 4-6 hours.

4. A method for recovering precious metals from sodium thiosulfate filter press residue according to claim 1, characterized in that: The concentration of hydrochloric acid in step (4) is 15-20%.

5. A method for recovering precious metals from sodium thiosulfate filter press residue according to claim 1 or 6, characterized in that: In step (4), hydrochloric acid is added in a ratio of 1:8-10 to the volume of the filtrate obtained in step (3).

6. A method for recovering precious metals from sodium thiosulfate filter press residue according to claim 1, characterized in that: The noble metal precipitate described in step (4) includes noble metal chloride.

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