A method of extracting palladium

Abstract

The present application relates to a kind of methods for extracting palladium, the method includes the following steps: (1) the palladium-containing material is mixed with nitric acid and catalyst containing alkali metal ions to obtain mixed solution, after heating reaction, residue is separated, and the palladium-containing leaching solution is obtained;(2) the palladium-containing leaching solution obtained in step (1) is separated and extracted to obtain metal palladium or palladium-containing product, and the remaining solution after separation is recycled to step (1).The catalyst containing alkali metal ions of the present application can make the reaction speed of palladium leaching faster than using pure nitric acid of the same concentration, and itself does not volatilize loss, thereby realizing the recycling of mother liquor;The method is simple in operation, low in production cost, greatly shortens the time for extracting palladium, does not produce secondary pollution, and meets the requirements of green environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to the production technology of hydrometallurgical extraction of palladium, and more particularly to a method for extracting palladium. Background Technology

[0002] Palladium, belonging to the platinum group metals, possesses excellent plasticity, stability, and catalytic activity, and is widely used in aerospace, nuclear energy, electronics, and catalysts. With global economic development, the global demand for palladium is increasing, but global palladium reserves are extremely scarce. Primary palladium ores have low palladium content and high extraction costs, while secondary palladium resources are more concentrated, have fewer impurities, and are relatively easier to recover. Therefore, recovering palladium from secondary palladium resources is of significant importance and has high economic value.

[0003] Palladium is chemically stable, slightly soluble in dilute nitric acid and hydrochloric acid, and insoluble in sulfuric acid. In industrial production, hot concentrated nitric acid or aqua regia (nitric acid and hydrochloric acid in a 1:3 ratio) is commonly used to dissolve palladium. However, concentrated nitric acid is volatile, and the reaction is violent, producing large amounts of nitrogen oxides. Aqua regia is highly corrosive, requiring high corrosion resistance in equipment, and the reaction generates large amounts of toxic gases, failing to meet environmental protection requirements. In recent years, researchers have been working to find alternative solvents to concentrated nitric acid or aqua regia.

[0004] CN109957659A discloses a method for recovering palladium from palladium-containing waste catalysts. The method includes the following steps: (1) adding the palladium-containing waste catalyst to water and boiling it at 90-100℃ for 1-2 hours, repeating the boiling 5-7 times, and then removing the solid; (2) boiling the solid obtained in step (1) with 1-3% alkaline solution at 85-95℃ for 1-2 hours, repeating the alkaline boiling 2-4 times; (3) after alkaline boiling, adjusting the pH of the solution to 1-3 with sulfuric acid, then adding 4-6 mol / L hydrochloric acid and a certain amount of sodium chlorate or chlorine as an oxidant, and leaching at 60-80℃ for 2-3 hours to obtain palladium-containing organic precipitate. The method has a high palladium recovery rate and low energy consumption, but the palladium extraction steps are complex and require a large amount of water. The reaction process requires a large amount of hydrochloric acid, and the highly corrosive and toxic chlorine and sodium chlorate cause environmental harm.

[0005] CN108285978A discloses a method for recovering palladium from a palladium-containing catalyst. The method involves removing organic matter from the catalyst through low-temperature distillation (150-350℃), followed by oxidative leaching of palladium in an HCl + NaCl solution using H₂O₂. The resulting palladium-containing leachate is then reduced with formic acid to obtain elemental palladium. While this method achieves a high palladium leaching rate, it consumes large amounts of hydrochloric acid and hydrogen peroxide during the reaction, generating highly volatile and toxic chlorine gas, resulting in severe environmental pollution.

[0006] Given the problems with the above-mentioned process, there is an urgent need to develop an environmentally friendly, economical, and efficient method for extracting palladium. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for extracting palladium. This method features low acid consumption, simple composition, low production cost, and a recyclable leaching system. It reduces acid consumption at the source, minimizes the introduction of impurity ions, improves atom utilization, generates no waste liquid, and achieves a high palladium leaching rate and fast leaching speed, demonstrating promising prospects for industrial application.

[0008] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0009] This invention provides a method for extracting palladium, the method comprising the following steps:

[0010] (1) The palladium-containing material is mixed with nitric acid and a catalyst containing alkali metal ions to obtain a mixed solution. After heating and reacting, the residue is separated to obtain a palladium-containing leachate.

[0011] (2) The palladium-containing leachate obtained in step (1) is separated and extracted to obtain metallic palladium or palladium-containing products. The remaining solution after separation is reused in step (1).

[0012] In this invention, the catalyst containing alkali metal ions can accelerate the leaching reaction of palladium and does not volatilize or lose its own value, thus enabling the recycling of the mother liquor. The catalyst containing alkali metal ions and palladium-containing materials are heated under nitric acid conditions. The leachate is separated and extracted to obtain metallic palladium or palladium-containing products. The remaining solution after separation can be reused in step (1). Using a mixture of the catalyst containing alkali metal ions and nitric acid instead of concentrated nitric acid and aqua regia for leaching palladium-containing materials significantly reduces acid consumption and the introduction of impurity ions. It also avoids the problem of volatilization and decomposition of reactants such as chloride ions, chlorine, and hydrogen peroxide in traditional recycling processes, which prevents recycling. This significantly reduces production costs and wastewater discharge, meeting the requirements of green environmental protection. These advantages constitute the greatest innovation of this invention compared to existing methods.

[0013] As a preferred embodiment of the present invention, the alkali metal ions in step (1) include Li + Na + or K + Any one of them, preferably Lⅰ + .

[0014] In this invention, Li + Na + or K + Ions, acting as catalysts, can significantly increase the leaching rate of palladium.

[0015] In this invention, the catalyst containing alkali metal ions in step (1) can be lithium nitrate, lithium sulfate, lithium chloride, sodium nitrate, sodium sulfate, sodium chloride, potassium nitrate, potassium sulfate, potassium chloride, lithium carbonate, potassium carbonate, sodium carbonate, or other compounds containing these alkali metal ions and their solutions.

[0016] As a preferred technical solution of the present invention, the concentration of alkali metal ions in the mixture in step (1) is ≥1 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L or 7 mol / L, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably ≥5 mol / L.

[0017] As a preferred technical solution of the present invention, the palladium content in the palladium-containing material in step (1) is ≥100ppm, for example, it can be 100ppm, 120ppm, 140ppm, 160ppm, 180ppm, 200ppm, 300ppm, 1000ppm, or even pure metallic palladium, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In this invention, the palladium-containing material in step (1) includes any one or at least two combinations of palladium metal, palladium alloy, palladium compound, palladium-containing mineral or palladium-containing secondary resource. Typical but non-limiting examples of such combinations include: a combination of palladium powder and palladium-containing mineral, a combination of palladium-containing mineral and palladium-containing secondary resource, or a combination of palladium-containing secondary resource and palladium powder, etc.

[0019] As a preferred technical solution of the present invention, the hydrogen ion concentration in the mixture in step (1) is ≥1 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L or 7 mol / L, etc., but is not limited to the listed values. Other achievable values ​​not listed within the value range are also applicable.

[0020] In this invention, the proportions of various materials in step (1) are not limited and can be adjusted according to actual conditions and needs.

[0021] As a preferred technical solution of the present invention, the temperature of the heating reaction in step (1) is ≥40℃, for example, it can be 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably ≥60℃.

[0022] As a preferred technical solution of the present invention, the separation and extraction method in step (2) includes, but is not limited to, electrolysis, extraction separation, ion exchange, adsorption separation or evaporation crystallization.

[0023] As a preferred technical solution of the present invention, the separation and extraction method in step (2) is preferably to electrolyze the palladium-containing leachate obtained in step (1), obtain metallic palladium at the cathode, and reuse the electrolyzed solution in step (1).

[0024] In this invention, the extraction and separation involves adding a certain amount of extractant to the palladium-containing leachate for extraction and back-extraction to obtain a relatively pure palladium-containing compound solution and a raffinate containing alkali metal ions. The extractant can be any one of diisopentyl sulfide (S201), sulfoxide, or hydroxyoxime, but is not limited to these extractants.

[0025] In this invention, the ion exchange and adsorption separation involves passing the palladium-containing leachate through a device filled with ion exchange resin or adsorbent to separate palladium from the catalyst-containing mother liquor, thereby obtaining a palladium-containing compound product. The ion exchange resin includes any one of isothiourea resin, chelated piperidine resin (R410), or extraction resin, and the adsorbent can be activated carbon, copper powder, etc., but is not limited to the above materials.

[0026] In this invention, the evaporation crystallization involves separating the catalyst and palladium from the palladium-containing leachate through heating and evaporation crystallization to obtain a palladium-containing compound product. The evaporation crystallization method includes rotary evaporation or multi-effect evaporation (MVR).

[0027] As a preferred technical solution of the present invention, the method includes the following steps:

[0028] (1) Mix palladium-containing materials with a palladium content ≥100ppm with Li-containing materials. + Na + or K + The catalyst (concentration ≥1mol / L) and nitric acid with hydrogen ion concentration ≥1mol / L were mixed, and then the mixture was heated at ≥40℃ to react and the residue was separated to obtain a palladium-containing leachate.

[0029] (2) The palladium-containing leachate obtained in step (1) is separated and extracted to obtain metallic palladium or palladium-containing products. The remaining solution after separation is reused in step (1) to realize the recycling of mother liquor.

[0030] In this invention, the solution separated in step (2) is reused in step (1) to achieve mother liquor recycling and reduce waste liquid discharge.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The catalyst containing alkali metal ions used in this invention can accelerate the reaction rate of palladium leaching, and it does not volatilize or lose itself, thus enabling the recycling of the mother liquor;

[0033] (2) Since there is no need to use chlorine-containing compounds as catalysts, the present invention can prepare metallic palladium or palladium compounds without chloride ions. The process is simple, the product quality is good, and no toxic chlorine gas is produced.

[0034] (3) The remaining solution after separation and extraction of the present invention can be recycled by adding nitric acid, or nitric acid can be generated at the anode through the electrolysis of the leachate. No waste liquid is generated in the whole process. Detailed Implementation

[0035] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0036] Example 1

[0037] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0038] (1) 79g of palladium powder (palladium content is 95%) was mixed with a solution containing 1.5 mol / L lithium nitrate and 6 mol / L nitric acid, and the mixture was heated and leached at 80°C. The residue was separated to obtain a palladium-containing leachate.

[0039] (2) The palladium-containing leachate obtained in step (1) is evaporated, concentrated, separated and crystallized to obtain palladium nitrate product, and the remaining mother liquor is recycled for step (1).

[0040] Example 2

[0041] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0042] (1) Mix 3.5g palladium powder (palladium content is 87%) and 0.16 mol lithium carbonate solid, add nitric acid to the solution to reduce the H+. + The concentration was adjusted to 1 mol / L and Li + The concentration was 1 mol / L, and then the leaching was carried out by heating at 80℃. The residue was separated to obtain a palladium-containing leachate.

[0043] (2) The palladium-containing leachate obtained in step (1) is electrolyzed to obtain pure metallic palladium at a current density of 100 A / m. 2 The remaining solution after electrolysis is reused in step (1).

[0044] Example 3

[0045] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0046] (1) Mix 100g of anode mud with a palladium content of 100ppm with a solution containing 7mol / L sodium nitrate and 1.3mol / L nitric acid, heat and leach at 60℃, and separate the residue to obtain palladium-containing leachate;

[0047] (2) The palladium-containing leachate obtained in step (1) is adsorbed and replaced with copper powder to obtain palladium metal deposits, and the remaining solution is reused in step (1).

[0048] Example 4

[0049] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0050] (1) Mix 3.8g of palladium powder (palladium content is 99.95%) with a solution containing 5mol / L potassium nitrate, 1mol / L lithium nitrate and 1.0mol / L nitric acid, heat and leach at 40℃, and separate the residue to obtain palladium-containing leachate;

[0051] (2) Electrolyze the palladium-containing leachate obtained in step (1) to obtain sponge palladium at a current density of 500 A / m. 2 The remaining solution after electrolysis is replenished with nitric acid and then reused in step (1).

[0052] Example 5

[0053] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0054] (1) 150g of alumina-palladium catalyst containing 0.3% palladium was mixed with a solution containing 6mol / L lithium nitrate and 1.5mol / L nitric acid, and the mixture was heated and leached at 50°C. The residue was separated to obtain a palladium-containing leachate.

[0055] (2) The palladium-containing leachate obtained in step (1) is added to diisoamyl sulfide (S201) for extraction. The raffinate is recycled to step (1). The organic phase is back-extracted to obtain palladium nitrate product.

[0056] Example 6

[0057] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0058] (1) Mix 100g of alumina-palladium catalyst containing 0.5% palladium with a solution containing 6mol / L sodium nitrate and 1.8mol / L nitric acid, heat and leach at 60℃, and separate the residue to obtain palladium-containing leachate;

[0059] (2) Pass the palladium-containing leachate obtained in step (1) through a chelated piperidine resin R410 adsorption column, then wash with dilute hydrochloric acid and elute with thiourea to obtain a high-purity palladium salt product. The remaining solution is reused in step (1).

[0060] Example 7

[0061] The only difference between this embodiment and embodiment 6 is that in step (2), activated carbon is used to adsorb palladium in the leachate, and after washing and drying, palladium-carbon composite material is obtained. All other conditions are the same as in embodiment 7.

[0062] Example 8

[0063] This embodiment provides a method for extracting palladium, the method comprising the following steps:

[0064] (1) Mix 1.04 g of palladium powder (palladium content is 99.95%) with a solution containing 6 mol / L lithium nitrate and 1 mol / L nitric acid, heat and leach at 80 °C, and separate the residue to obtain palladium-containing leachate;

[0065] (2) The palladium-containing leachate obtained in step (1) is electrolyzed to obtain pure metallic palladium at a current density of 400 A / m. 2 The remaining solution after electrolysis is reused in step (1).

[0066] Example 9

[0067] The only difference between this embodiment and embodiment 8 is that the lithium nitrate concentration in the solution in step (1) is 0.5 mol / L, while all other conditions are the same as in embodiment 8.

[0068] Example 10

[0069] The only difference between this embodiment and embodiment 8 is that the heating leaching temperature in step (1) is 30°C, while all other conditions are the same as in embodiment 8.

[0070] Example 11

[0071] The only difference between this embodiment and Example 8 is that the concentration of nitric acid in the solution in step (1) is 0.5 mol / L, while all other conditions are the same as in Example 8.

[0072] Comparative Example 1

[0073] This comparative example provides a method for extracting palladium, which includes the following steps: (1) mixing 1.04 g of palladium powder (palladium content is 99.95%) with 7 mol / L nitric acid, heating and leaching at 80°C, separating the residue to obtain palladium-containing leachate, and other conditions being the same as in Example 8.

[0074] Comparative Example 2

[0075] This comparative example provides a method for extracting palladium, which includes the following steps: (1) mixing 1.04 g of palladium powder (palladium content is 99.95%) with a solution containing 7 mol / L lithium nitrate, heating and leaching at 80°C, separating the residue to obtain a palladium-containing leachate, and other conditions being the same as in Example 8.

[0076] The concentration of palladium in the palladium-containing leachate was tested using inductively coupled plasma atomic emission spectrometry. The leaching time for both Examples 1-11 and Comparative Examples 1-2 was 5 h. The leaching rates of palladium in Examples 1-11 and Comparative Examples 1-2 are shown in Table 1.

[0077] Table 1

[0078]

[0079] As can be seen from Table 1, the method of the present invention can efficiently extract palladium. In Examples 1-8, the palladium nitrate leaching rate is greater than 91%. In Example 9, the palladium extraction method has a lower leaching rate and palladium recovery rate because the concentration of alkali metal ions in the solution in step (1) is low and the catalytic effect is poor. In Example 10, the palladium extraction method has a lower leaching temperature in step (1) because the leaching reaction is incomplete, resulting in a decrease in the palladium nitrate leaching rate and palladium recovery rate. In Example 11, the palladium extraction method has a lower leaching rate and palladium recovery rate because the acidity in the solution in step (1) is insufficient and the oxidizing ability is weak.

[0080] Comparative Example 1 used a system containing 7 mol / L HNO3 to leach palladium. After 5 hours of heating and leaching, the palladium leaching rate was only 0.6%, indicating a very slow leaching rate and the generation of a large amount of waste acid solution. In Example 8, using the same amount of 6 mol / L lithium nitrate solution and 1 mol / L nitric acid at the same temperature, the palladium leaching rate was 99.6% after 5 hours of heating and leaching, showing that the addition of lithium ions had a good catalytic effect. Comparative Example 2 used a system containing 7 mol / L lithium nitrate to leach palladium, but no palladium leaching was achieved after 5 hours of heating and leaching, indicating that acidic conditions are a necessary condition for palladium leaching.

[0081] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for extracting palladium, characterized in that, The method includes the following steps: (1) The palladium-containing material is mixed with nitric acid and a catalyst containing alkali metal ions to obtain a mixed solution. After heating and reacting, the residue is separated to obtain a palladium-containing leachate. The alkali metal ions mentioned include any one of Li+, Na+ or K+; (2) The palladium-containing leachate obtained in step (1) is separated and extracted to obtain metallic palladium or palladium-containing products. The remaining solution after separation is reused in step (1).

2. The method according to claim 1, characterized in that, The alkali metal ion mentioned in step (1) is Lⅰ. + .

3. The method according to claim 1, characterized in that, The concentration of alkali metal ions in the mixture in step (1) is ≥1 mol / L.

4. The method according to claim 3, characterized in that, The concentration of alkali metal ions in the mixture in step (1) is ≥5 mol / L.

5. The method according to claim 1, characterized in that, The palladium content in the palladium-containing material in step (1) is ≥100ppm.

6. The method according to claim 1, characterized in that, The hydrogen ion concentration in the mixture in step (1) is ≥1 mol / L.

7. The method according to claim 1, characterized in that, The temperature of the heating reaction in step (1) is ≥40℃.

8. The method according to claim 7, characterized in that, The heating reaction in step (1) is at a temperature of ≥60℃.

9. The method according to claim 1, characterized in that, The separation and extraction methods described in step (2) include electrolysis, extraction separation, ion exchange, adsorption separation, or evaporation crystallization.

10. The method according to claim 1, characterized in that, The separation and extraction method described in step (2) is to electrolyze the palladium-containing leachate obtained in step (1), obtain metallic palladium at the cathode, and reuse the electrolyzed solution in step (1).

11. The method according to claim 1, characterized in that, The method includes the following steps: (1) A palladium-containing material with a palladium content ≥100ppm is mixed with nitric acid containing alkali metal ions and a hydrogen ion concentration ≥1mol / L to obtain a mixed solution. After reacting at ≥40℃, the residue is separated to obtain a palladium-containing leachate. The alkali metal ions include Li + Na + or K + Any one of the following; the concentration of alkali metal ions in the mixture is ≥1 mol / L; (2) The palladium-containing leachate obtained in step (1) is separated and extracted to obtain metallic palladium or palladium-containing products. The remaining solution after separation is reused in step (1) to realize the recycling of mother liquor.

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