Method for recovering platinum in nickel-platinum waste

Abstract

The invention relates to a method for recovering platinum in nickel-platinum waste. The method comprises the steps of hot nitric acid dissolution, filtration, pH adjustment, selective precipitation and drying. The characteristic that hot nitric acid can completely dissolve Ni and partially dissolve Pt is utilized to achieve preliminary separation of NiPt, sodium sulfide is used as a precipitator, selective precipitation of platinum is achieved through the Ksp difference of platinum sulfide and base metal sulfide within the pH range of 1-2, the recovery rate of platinum is greatly increased, and energy consumption of the platinum recovery process is reduced. Emission of a large amount of volatile acid is avoided while economic benefits are improved, and the method is more suitable for actual production.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and in particular to a method for recovering platinum from nickel-platinum waste. Background Technology

[0002] In modern industry, the recycling of platinum-containing waste typically employs aqua regia dissolution-ammonium chloride precipitation platinum process. This involves dissolving the solid material in aqua regia, followed by ammonia denitration and ammonium chloride precipitation to obtain ammonium chloroplatinate precipitate. After filtration and separation, the precipitate is calcined to obtain sponge platinum. For example, Chinese patent CN115418481A discloses a method for recovering platinum and nickel from waste nickel-platinum targets, in which the main reactions are as follows: 3Pt+4HNO3+18HCl→3H2PtCl6+4NO↑+8H2O 2NH3 + HNO3 → N2 + 3H2O + 2NO2 + 2HCl H2PtCl6+2NH4Cl→(NH4)2PtCl6↓+2HCl 3(NH4)2PtCl6→3Pt+2N2↑+2NH4Cl+16HCl↑

[0003] In the actual operation of the above recycling process, nitrogen oxides, hydrochloric acid and other acidic volatile gases will be generated. Therefore, an absorption system for volatile acids and other tail gases is required. In addition, the calcination process has high energy consumption and the obtained sponge platinum contains a lot of impurities (such as iron, copper and nickel), so it still needs to be further refined and purified.

[0004] Chinese patent CN110387467A discloses a process for separating and purifying sponge platinum from platinum-containing materials. Although the crude platinum powder is dissolved by adding concentrated hydrochloric acid and concentrated nitric acid in sequence, it is essentially based on the principle of aqua regia dissolution and will also produce acidic gas.

[0005] Therefore, a recycling method with higher recycling rate, green environmental protection, energy saving and emission reduction is needed. Summary of the Invention

[0006] A primary objective of this invention is to provide a method for recovering platinum from nickel-platinum waste, which can improve economic efficiency while avoiding the emission of large amounts of volatile acids.

[0007] To achieve the above-mentioned objective, this invention provides a method for recovering platinum from nickel-platinum waste, comprising the following steps: S1. Hot nitric acid dissolution: Take nickel-platinum waste, add sufficient concentrated nitric acid, stir and heat to dissolve, leaving a precipitate; S2. Filtration: The precipitate is filtered out to obtain a first solution and filter residue. The filter residue is washed and dried to obtain platinum powder with a purity >99%. S3. Adjust pH: Slowly add sodium hydroxide to the first solution and adjust the pH to 1-2 while stirring to obtain the second solution; S4. Selective precipitation: Sodium sulfide is slowly added to the second solution and stirred thoroughly to produce a precipitate, which is then filtered to obtain the second filter residue. S5. Drying: The second filter residue is filtered, washed, and dried to obtain platinum sulfide.

[0008] Specifically, in step S1, the volume ratio of nitric acid to water in the concentrated nitric acid is 1:1, and the dosage is 40 mL of concentrated nitric acid per 1 g of nickel-platinum waste.

[0009] Specifically, in step S1, the heating temperature is 60-80℃ and the reaction time is 2-2.5 hours.

[0010] Specifically, step S4 uses an 8wt% sodium sulfide solution at a flow rate of 12 mL / min.

[0011] Specifically, in step S4, the pH is maintained within the range of 1-2.

[0012] The beneficial effects of the technical solution of this invention are: 1. This invention eliminates the need for aqua regia system and processes such as ammonia denitrification, ammonium chloride platinum precipitation, and high-temperature calcination, thereby eliminating the generation of toxic exhaust gases such as hydrogen chloride and nitrogen oxides. It also eliminates the need for an exhaust gas absorption system, significantly reducing environmental treatment costs.

[0013] 2. Using sodium sulfide as a precipitant, selective precipitation of platinum is achieved by taking advantage of the difference in Ksp between platinum sulfide and base metal sulfides in the pH range of 1-2, which greatly improves the platinum recovery rate and reduces the energy consumption of the platinum recovery process. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of a method for recovering platinum from nickel-platinum waste according to the present invention. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments.

[0016] Example: like Figure 1 As shown, a method for recovering platinum from nickel-platinum waste includes the following steps: S1. Hot Nitric Acid Dissolution: Take nickel-platinum waste, add sufficient concentrated nitric acid, stir and heat to dissolve, leaving a precipitate. The volume ratio of nitric acid to water in the concentrated nitric acid is 1:1, and the dosage is 40 mL of concentrated nitric acid per 1 g of nickel-platinum waste. The heating temperature is 60-80℃, and the reaction time is 2-2.5 hours.

[0017] The actual sample size of nickel-platinum waste is 500g, and the amount of concentrated nitric acid used is 20L. The main reaction that occurs in this step is: 2HNO3 + Ni → Ni(NO3)2 + H2↑ 4HNO3 + Pt → Pt(NO3)4 + 2H2↑ Unlike the method of generating complex ions in aqua regia, both nickel and platinum dissolve in concentrated nitric acid upon heating, yielding nitrates. While this method alone cannot completely separate the two, nickel reacts faster and dissolves completely within a suitable timeframe, while platinum reacts very slowly. After the nickel dissolves, the undissolved platinum precipitates. The undissolved platinum can be directly recovered, resulting in high-purity platinum powder after filtration and separation. Approximately 33% of the platinum remains in the liquid as Pt(NO3)4. This process eliminates the need for the aqua regia system, ammonia denitrification, ammonium chloride precipitation of platinum, and high-temperature calcination, thus eliminating the generation of toxic exhaust gases such as hydrogen chloride and nitrogen oxides. It also eliminates the need for an exhaust gas absorption system, significantly reducing environmental remediation costs.

[0018] S2. Filtration: The precipitate is filtered out to obtain the first solution and filter residue. After washing and drying the filter residue, platinum powder with a purity >99% is obtained.

[0019] The precipitated platinum powder can be directly filtered out of the solution system, and after simple washing and drying, high-purity platinum powder is obtained. However, the first solution contains a large amount of Ni(NO3)2 and Pt(NO3)4, which need to be separated.

[0020] S3. Adjust pH: Slowly add sodium hydroxide to the first solution and adjust the pH to 1-2 while stirring to obtain the second solution.

[0021] Sodium hydroxide is only used to control the pH of the solution, in order to create an environment that is conducive to platinum precipitation and avoids nickel precipitation.

[0022] S4. Selective Precipitation: Sodium sulfide is slowly added to the second solution and stirred thoroughly to produce a precipitate. The precipitate is then filtered to obtain the second filter residue. In step S4, the pH is maintained within the range of 1-2. An 8 wt% sodium sulfide solution is used at a flow rate of 12 mL / min.

[0023] Sodium sulfide is used as a precipitant in this step, and the main reaction that occurs in this step is: Pt(NO3)4+2Na2S→PtS2↓+4NaNO3 The second solution contains a large amount of nickel ions. Within a specific pH range, sodium sulfide can selectively precipitate Pt while nickel does not precipitate, thus allowing platinum and nickel to be separated relatively completely. Platinum enters the precipitate as platinum sulfide, thereby separating from the solution system. This effectively reduces separation costs.

[0024] S5. Drying: Filter and wash the second filter residue, and dry it to obtain platinum sulfide.

[0025] This invention utilizes the characteristic that hot nitric acid can completely dissolve Ni and partially dissolve Pt to achieve preliminary separation of Ni and Pt. Sodium sulfide is used as a precipitant, and the difference in Ksp between platinum sulfide and base metal sulfides within the pH range of 1-2 enables selective precipitation of platinum, significantly improving platinum recovery rate and reducing energy consumption in the platinum recovery process. While improving economic efficiency, it avoids the emission of large amounts of volatile acid, making it more suitable for actual production.

[0026] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for recovering platinum from nickel-platinum waste, characterized in that... The steps include: S1. Hot nitric acid dissolution: Take nickel-platinum waste, add sufficient concentrated nitric acid, stir and heat to dissolve, leaving a precipitate; S2. Filtration: The precipitate is filtered out to obtain a first solution and filter residue. The filter residue is washed and dried to obtain platinum powder with a purity >99%. S3. Adjust pH: Slowly add sodium hydroxide to the first solution and adjust the pH to 1-2 while stirring to obtain the second solution; S4. Selective precipitation: Sodium sulfide is slowly added to the second solution and stirred thoroughly to produce a precipitate, which is then filtered to obtain the second filter residue. S5. Drying: The second filter residue is filtered, washed, and dried to obtain platinum sulfide.

2. The method for recovering platinum from nickel-platinum waste according to claim 1, characterized in that: In step S1, the volume ratio of nitric acid to water in the concentrated nitric acid is 1:1, and the dosage is 40 mL of concentrated nitric acid per 1 g of nickel-platinum waste.

3. The method for recovering platinum from nickel-platinum waste according to claim 1, characterized in that: In step S1, the heating temperature is 60-80℃ and the reaction time is 2-2.5 hours.

4. The method for recovering platinum from nickel-platinum waste according to claim 1, characterized in that: Step S4 uses an 8wt% sodium sulfide solution at a flow rate of 12 mL / min.

5. The method for recovering platinum from nickel-platinum waste according to claim 1, characterized in that: In step S4, the pH is maintained within the range of 1-2.

Images