A method for selectively leaching and recovering palladium from waste palladium-plated parts

Abstract

The invention discloses a method for selectively leaching and recovering palladium from waste palladium-plated parts. The method uses waste palladium-plated parts as raw materials, uses a low eutectic system as a leaching solution to carry out a leaching reaction, filters after the leaching is completed, adds dimethylglyoxime precipitant to the leaching solution to precipitate the palladium in the leaching solution, filters after the precipitation is completed, and obtains dimethylglyoxime palladium and a filtrate. The invention has simple process, convenient operation, short leaching time, low cost, and adopts a non-toxic, biodegradable low eutectic green solvent, which can selectively leach palladium from palladium-plated parts, avoids the use of a large amount of toxic solvents such as strong acids, and also reduces the reduction of other substances, thereby reducing the difficulty of subsequent metal separation. Green and efficient recovery of metallic palladium is achieved.

Description

Technical Field

[0001] The invention relates to a method for selectively leaching and recovering palladium in waste palladium-plated parts, belonging to the technical field of metal recovery and solid waste resource utilization. Background Art

[0002] As a precious metal with good high temperature resistance, corrosion resistance and stable electrical properties, palladium has been widely used in many fields such as electronics, medicine, and chemical catalysts. For example, palladium carbon catalysts are widely used in the petrochemical and pharmaceutical industries, and platinum palladium rhodium catalysts with cordierite as carriers are used in automobile exhaust catalysts, which are of great significance for protecting the environment.

[0003] At present, the relatively mature processes for palladium recovery in production mainly include: carrier dissolution method, using acid or alkali to dissolve the carrier to obtain slag containing palladium, and extracting palladium after roasting and dissolving the filter residue; chlorine volatilization method, using chlorine to chlorinate palladium under heating conditions, palladium absorbs and extracts palladium after volatilization in the form of chloride; selective dissolution method, using inorganic solvents to dissolve palladium while the carrier does not dissolve, and extracting palladium from the solution; full dissolution method, controlling strong leaching conditions and oxidizing atmosphere, so that the palladium in the carrier and catalyst is dissolved into the solution at the same time, and then palladium is extracted from the solution. Fire smelting method, smelting the carrier at high temperature to form slag, palladium enters the collector and is concentrated at the bottom of the furnace for recovery. Or the material is mixed with non-ferrous metal concentrate, and palladium is recovered from the anode mud obtained by electrolysis; incineration method, incinerating the carrier, dissolving the ash with aqua regia and extracting palladium. When these methods either produce huge pollution during the reaction; or the reaction conditions are relatively complex, the instrument requirements are high, and the operation is difficult; or the recovery rate is low. Therefore, it is of great significance to explore a green leaching recovery system for selectively dissolving palladium in waste palladium-plated parts.

[0004] Prior to this, we applied for a method for selective leaching and precipitation to recover palladium from printed circuit boards (application number: 2021105041737). In this invention, we used DMF as the main leaching agent. As a polar aprotic organic solvent, DMF has certain environmental advantages compared to previous strong acids and alkalis, but it also has the basic harmfulness of organic solvents and still has certain pollution to the environment and human health. The present invention uses the leaching agent in a previous method for selective leaching to recover silver on the surface of discarded silver-plated parts or silver-containing solid waste, which belongs to a low eutectic leaching system. In the present invention, a low eutectic solvent is used to replace the traditional solvent DMF, aiming to make the process greener and safer, and to minimize harmful emissions or the use of strong oxidants. Different from the patent for selective leaching to recover discarded silver-plated parts, the present invention differs from it in that the recovery objects are different, and the recovery methods of the invention are different. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for selectively leaching and recovering palladium in palladium-plated parts in electronic waste using a low-eutectic-chloride system; the present invention adopts a selective leaching method, which can selectively leach palladium in palladium-plated parts in electronic waste to obtain high-purity compound palladium, which is of great significance for the recovery of precious metals, avoids the use of strong acids or cyanides and other reagents with serious secondary pollution and high toxicity, making the recovery process green and pollution-free.

[0006] The technical solution of the present invention is achieved in this way.

[0007] The present invention provides a method for selectively leaching and recovering palladium from palladium-plated parts in electronic waste, and the specific steps are as follows:

[0008] A mixed solution consisting of an inorganic chloride salt and a low eutectic solvent is used as a leaching solution, and waste palladium-plated parts are added into the leaching solution according to a solid-liquid mass volume ratio of 1:10-1:30 g / mL for leaching reaction, the leaching temperature is 40-90°C, the leaching time is 10-60 minutes, and after the leaching is completed, a first filtrate and a filter residue are obtained by filtering; then, a dimethylglyoxime ethanol solution is added to the first filtrate to precipitate palladium ions in the filtrate, and after the precipitation is completed, a second filtrate and dimethylglyoxime palladium are obtained by filtering, the palladium is recovered, and the second filtrate is recycled.

[0009] In the present invention, the solid-liquid mass volume ratio of the mixed solution composed of the waste palladium-plated parts, the inorganic chloride salt and the low eutectic solvent is 1:10-1:20 g / mL, the leaching temperature is 80-90° C., and the leaching time is 10-30 min.

[0010] In the present invention, the inorganic chloride salt is one or more of anhydrous cupric chloride, dihydrate cupric chloride and ferric chloride.

[0011] In the present invention, the concentration of the inorganic chloride salt in the mixed solution is 0.25-1.5 mol / L.

[0012] In the present invention, the deep eutectic solvent is any one or more of choline chloride-urea, choline chloride-propylene glycol, choline chloride-oxalic acid, choline chloride-glycerol, and choline chloride-ethylene glycol.

[0013] In the present invention, the volume ratio of deionized water to the first filtrate is 0.5:1-2:1, and the precipitation time is 0.5-1.5h.

[0014] In the present invention, the concentration of the dimethylglyoxime ethanol solution is 0.1 mol / L, and the amount of the dimethylglyoxime ethanol solution added is 60% of the volume of the leaching solution.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The invention has simple process, convenient operation, short leaching time, low cost, and adopts non-toxic, biodegradable low eutectic green solvent, which can selectively leach palladium from waste palladium-plated parts, avoids the use of a large amount of toxic solvents such as strong acid, and also reduces the reduction of other substances, thereby reducing the difficulty of subsequent metal separation, thereby realizing green and efficient recovery of metal palladium. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a process flow chart of a method for selectively leaching and recovering palladium from palladium-plated parts of electronic waste.

[0018] Figure 2 Energy spectrum analysis of the electron microscope image of Example 1.

[0019] Figure 3 Experimental comparison diagram of Example 1. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] Example 1 Palladium-plated part 1

[0022] After digestion, the waste palladium-plated parts contain 0.1% palladium, 2.1% nickel and 5.4% copper. Figure 1 As shown: 2.5g of waste palladium-plated parts are placed in 25mL of choline chloride-ethylene glycol liquid solvent containing 1.5mol / L copper chloride dihydrate (solid-liquid mass ratio is 1:10g / mL), and heated in a water bath at a temperature of 90°C. Leaching for 10min, filtering after leaching, the filtrate includes copper ions, palladium ions and nickel ions, and palladium, copper and nickel are all divalent. The content of palladium is 0.0025g, the content of copper is 0.135g, the content of nickel is 0.525g, and the leaching rate of palladium can reach 100%. 15mL of 0.1mol / L dimethylglyoxime ethanol solution is added to the filtrate, and the palladium ions in the filtrate are precipitated in the form of dimethylglyoxime palladium. After 1h of precipitation, dimethylglyoxime palladium is filtered to obtain dimethylglyoxime palladium, and the precipitation rate of palladium reaches more than 99.99%. In the detection of the precipitate, we did not find the peaks of Cu and other metals in the energy spectrum, demonstrating the high-purity selective recovery of palladium from waste palladium-plated parts by the low-eutectic-chloride system. Figure 2 The components contained in the precipitate of the reaction example 1 were found to be dimethylglyoxime palladium based on its material composition. Figure 3 It reflects the changes in the leaching of surface palladium during the leaching process of discarded palladium-plated parts. After 10 minutes of action, all the palladium in the surface coating has been dissolved.

[0023] Example 2 Palladium-plated part 2

[0024] After digestion, the palladium content of the waste palladium-plated parts was measured to be 0.003%, the nickel content was 0.06%, and the copper content was 0.15%. Figure 1 As shown, 5.1g of waste palladium-plated parts were placed in 100mL of choline chloride-urea liquid solvent containing 1.5mol / L copper chloride dihydrate (solid-liquid mass ratio of 1:20g / mL), heated in a water bath at 90°C, and leached for 10min. The copper, nickel, and palladium in the leachate were all present in the divalent form in the leachate, and the palladium content was: 1.5*10 -4 g, copper content: 7.6*10 -3 g, nickel content: 3.0*10 -3 g, wherein the leaching rate of palladium can reach 100%. After leaching, 60 mL of 0.1 mol / L dimethylglyoxime ethanol solution is added, and the precipitation time is 1 hour. After filtration and drying, palladium precipitate is obtained, wherein the precipitation rate of palladium reaches more than 99.99%.

[0025] Example 3 Palladium-plated part 3

[0026] After digestion, the palladium content in the discarded palladium-plated part 3 was measured to be 0.07%, the copper content was 3.5%, and the nickel content was 1.4%.

[0027] Extraction process such as Figure 1 As shown, 10g of waste palladium-plated parts are placed in 100mL of choline chloride-propylene glycol liquid solution containing 1.5mol / L anhydrous copper chloride (solid-liquid ratio is 1:10g / mL), heated in a water bath at 90°C, and leached for 10min. The palladium, nickel, and copper in the leaching solution are all present in the leaching solution in a divalent form, wherein the content of palladium is 0.007g, the content of copper is 0.35g, and the content of nickel is 0.14g, wherein the leaching rate of palladium can reach 100%. After the leaching is completed, 60mL of 0.1mol / L dimethylglyoxime ethanol solution is added, and the precipitation time is 1h. After filtration and drying, palladium precipitate is obtained, wherein the precipitation rate of palladium is more than 98.5%.

Claims

1. A method for selectively leaching and recovering palladium from waste palladium-plated parts, characterized in that: The specific steps are as follows: A mixed solution composed of an inorganic chloride salt and a low eutectic solvent is used as a leaching solution, and waste palladium-plated parts are added to the leaching solution according to a solid-liquid mass volume ratio of 1:10-1:30 g / mL for leaching reaction, the leaching temperature is 40-90°C, the leaching time is 10-60 minutes, and after the leaching is completed, a first filtrate and a filter residue are obtained by filtering; then, a dimethylglyoxime ethanol solution is added to the first filtrate to precipitate palladium ions in the filtrate, and after the precipitation is completed, a second filtrate and dimethylglyoxime palladium are obtained by filtering, the palladium is recovered, and the second filtrate is recycled; wherein: The inorganic chloride salt is anhydrous copper chloride or dihydrate copper chloride; The low eutectic solvent is any one or more of choline chloride-urea, choline chloride-propylene glycol, choline chloride-oxalic acid, choline chloride-glycerol, and choline chloride-ethylene glycol, wherein the molar ratio of choline chloride to another component is 1:

2.

2. The method according to claim 1, characterized in that The solid-liquid mass volume ratio of the mixed solution composed of the waste palladium-plated parts, the inorganic chloride salt and the low eutectic solvent is 1:10-1:20 g / mL, the leaching temperature is 80-90° C., and the leaching time is 10-30 min.

3. The method according to claim 1, characterized in that The concentration of inorganic chloride salt in the mixed solution is: 0.25-1.5mol / L.

4. The method according to claim 1, characterized in that: The concentration of dimethylglyoxime ethanol solution is 0.1 mol / L, and the amount of solution added is 60% of the volume of the leaching solution.

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