CN114959290A - Method for selectively leaching and recycling precious metal gold, silver and palladium in electronic waste step by step - Google Patents

Abstract

The invention discloses a method for selectively leaching and recovering precious metal gold, silver and palladium from electronic waste in steps. It uses the electronic waste powder containing gold, silver and palladium as the raw material, firstly adds the ionic liquid-chloride salt system to carry out the leaching reaction, and filters after the leaching is completed to obtain the first filtrate and filter residue; after adding deionized water to the first filtrate Filtration to obtain the second filtrate and a mixed precipitate of gold and silver, adding the diacetyl oxime solution to the second filtrate and filtering to obtain the third filtrate and the precipitation of diacetyl palladium. Adding a certain amount of calcium chloride solution to the gold-silver mixture and filtering to obtain the fourth filtrate and elemental gold, and finally adding water to the fourth filtrate and filtering to obtain silver chloride precipitation and the fifth filtrate. Finally, the third filtrate can be used for leaching after rotary evaporation. The invention has simple process, convenient operation, short leaching time, can selectively leaching gold, silver and palladium in electronic waste, and can realize green and efficient recovery of precious metal gold, silver and palladium.

Description

A method for selective leaching and step-by-step recovery of precious metal gold, silver and palladium in electronic waste

technical field

The invention relates to a method for selectively leaching and recovering precious metal gold, silver and palladium in electronic waste, belonging to the technical field of metal recovery and solid waste recycling.

Background technique

Because gold and silver have excellent stability and good electrical and thermal conductivity, gold and silver are used more and more widely in the electronics industry, such as the use of electroplating gold and silver high-frequency conductors and high-temperature Gold and silver alloys for welding. 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. Compared with gold, silver and palladium ores, the content of gold, silver and palladium in the waste containing gold, silver and palladium is higher, so it is of great significance to recover gold, silver and palladium from secondary resources.

At present, the methods for recovering gold, silver and palladium in production are as follows: nitric acid dissolution method, using nitric acid to dissolve alloy, silver and palladium entering the solution, using sodium chloride to precipitate silver, part of palladium in the form of Ag ₂ PdCl ₆ and AgCl co-precipitation, and chlorine Silver chemical adsorbs a large amount of palladium, which makes it difficult to separate silver and palladium; the concentrated sulfuric acid separation method, when the concentrated sulfuric acid dissolves silver, requires a higher temperature, and the dissolution effect of silver is poor, and most of the palladium also enters the solution, which not only affects the recovery of silver, but also affects The refining of gold and palladium, and the speed of dissolving silver in sulfuric acid is slow. Therefore, it is of great significance to explore a green leaching recovery system that selectively dissolves gold, silver and palladium in electronic waste.

In previous studies, we used DMF (N,N-dimethylformamide) to distribute and recover gold, silver, and palladium. However, because DMF is an organic reagent, it has a greater environmental friendly effect than strong acids and bases. , but it still has certain harm to the human body and the environment in essence.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for selectively leaching and recovering precious metal gold, silver and palladium in electronic waste based on an ionic liquid-chloride system; the present invention adopts a selective leaching method, which can Selectively leaching precious metals gold, silver and palladium from electronic waste to obtain high-purity gold, high-purity compound silver and high-purity compound palladium, which is of great significance for the recovery of precious metals and avoids the use of strong acids or cyanide and other serious secondary pollution , Highly toxic reagents make the recycling process green and pollution-free.

The present invention adopts the ionic liquid-chloride system selective leaching method to realize the recovery of precious metal gold, silver and palladium in electronic waste. Different from the previous DMF system, we have further optimized the leaching solvent. Ionic-like liquids have good environmental benefits and good stability. The reagent used in this patent can simultaneously recycle gold, silver and palladium in electronic waste, and can realize the distribution and extraction of three precious metals by adding deionized water, calcium chloride aqueous solution, precipitating agent, etc., so as to achieve the purpose of recycling .

The technical solutions of the present invention are as follows.

The invention provides a method for selectively leaching and recovering precious metal gold, silver and palladium in electronic waste, and the specific steps are as follows:

(1) The mixed solution composed of inorganic chloride salt and ionic liquid solvent is used as the leaching solution, and the electronic waste powder containing gold, silver and palladium is added to the leaching solution according to the solid-liquid mass volume ratio of 1:10-1:90g/mL Carry out leaching reaction, leaching temperature is 30-90 ℃, leaching time is 60-120min, after leaching is finished, filter to obtain first filtrate and filter residue;

(2) Add deionized water to the first filtrate to reduce the gold ions and silver ions in the precipitation filtrate. After the precipitation is completed, add 0.5-1mol/L calcium chloride solution to the system to dissolve the precipitated silver chloride. It is 20-80% of the leachate, and then filtered to obtain the fourth filtrate and elemental gold;

(3) continue to add water to precipitate silver ions in the 4th filtrate, filter to obtain the 5th filtrate and silver chloride;

(4) in the second filtrate, add the dimethylglyoxime precipitant to precipitate the reduced palladium, and filter after the reduction to obtain the dimethylglyoxime palladium and the third filtrate; above, realize gold elemental substance, silver chloride and dimethylglyoxime palladium respectively recovery, the third filtrate is recycled.

In the above step (1), the solid-liquid mass volume ratio of the mixed solution composed of the electronic waste powder containing gold, silver and palladium, the inorganic chloride salt and the ionic liquid solvent is 1:10-1:40 g/mL.

In the above step (1), the inorganic chloride salt is one or more of cupric chloride dihydrate, cupric chloride anhydrous, and ferric chloride; the concentration of the inorganic chloride salt in the mixed solution is: 0.25-1.5 mol/L; Class ionic liquid solvent is any one in choline chloride-urea, choline chloride-propylene glycol, choline chloride-oxalic acid, choline chloride-glycerol, choline chloride-ethylene glycol or more, wherein the molar ratio of choline chloride to another component is: 1:2.

In the above step (2), the volume ratio of deionized water to the first filtrate is 1:2-2:1, and the precipitation time is 0.5-1.5h.

In the above step (2), the added calcium chloride solution has a solubility of 0.5-1 mol/L, and the added amount is 20-80% of the volume of the leachate. The amount of calcium chloride added is related to the silver content in the electronic waste. With the addition of calcium chloride, the silver will redissolve.

In the above step (3), the volume of deionized water added to the second filtrate is equal to the volume of the leachate.

In the above-mentioned step (4), 0.1 mol/L-1 mol/L diacetyl oxime ethanol solution is added to the third filtrate to precipitate and reduce palladium, and the addition amount of diacetyl oxime ethanol solution is 40-100% of the volume of the leachate.

Compared with the prior art, the beneficial effects of the present invention are:

The invention has simple process, convenient operation, short leaching time, low cost and high recovery efficiency. The use of non-toxic and biodegradable ionic liquid-like green solvent can selectively leaching gold, silver and palladium in electronic waste, avoiding the use of a large amount of strong acids and other toxic solvents, and reducing the reduction of other substances and subsequent metals. Difficulty of separation. Achieve green and efficient recovery of precious metals gold, silver and palladium.

Description of drawings

1 is a process flow diagram of a method for selectively leaching and recovering precious metals gold, silver and palladium in electronic waste according to the present invention.

Figure 2. Energy spectrum analysis of the precipitated gold in Example 1.

Figure 3 Energy spectrum analysis of the precipitated compound silver in Example 1.

Figure 4 Energy spectrum analysis of the precipitated compound palladium in Example 1.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and implementation.

Example 1

After digestion and measurement, the electronic waste containing gold, silver and palladium contains 0.003% gold, 0.007% palladium, 0.01% silver, 11.5% copper, 2.8% nickel, and 2.8% iron. 1.3%. The extraction process is shown in Figure 1: put 0.33 g of electronic waste powder containing gold, silver and palladium into 10 mL of choline chloride-ethylene glycol liquid solvent containing 1.5 mol/L copper chloride (solid-liquid mass ratio is 1:30g/mL), heated in a water bath at 80°C. The leaching was carried out for 10 min, and after the leaching was completed, the mixture was filtered. In the first filtrate, gold was trivalent, palladium was bivalent, copper was bivalent, and silver was monovalent. 10 mL of deionized water was added to the first filtrate, followed by filtration to obtain the second filtrate and a mixed precipitate of gold and silver. The gold ions in the first filtrate will be reduced to gold element for precipitation, the silver ions will be precipitated in the form of silver chloride, and 5 mL of 0.6 mol/L calcium chloride solution is added to the precipitate. Will dissolve, filter out the gold element at this time, and filter to obtain the fourth filtrate and gold element; then add 10 mL of deionized water to the fourth filtrate to reduce the silver ions, and filter to filter out the silver chloride, The fifth filtrate and silver chloride were obtained; 6 mL of a 0.1 mol/L ethanolic solution of butanedione oxime was added to the second filtrate, and the palladium ions in the filtrate were precipitated in the form of palladium butanedione oxime. Filtration gave the fourth filtrate and palladium dimethylglyoxime. Finally, elemental gold, silver chloride and palladium dimethylglyoxime were obtained from the precipitate. Among them, the leaching rate of gold is over 99.7%, that of silver is over 99.7%, that of palladium is over 99.6%, that of copper is over 32.1%, that of nickel is over 19.3%, and that of iron is over 5.9%. %. The electron microscope energy spectrum analysis was performed on the precipitated gold, the precipitated silver chloride, and the precipitated dimethylglyoxime palladium respectively. Through the energy spectrum analysis, we found that in the detection of the precipitate, we did not find the peaks of other metals, showing that High-purity selective recovery of gold-silver-palladium from electronic waste powder containing gold-silver-palladium-like ionic liquid-chloride system.

Example 2

After digestion, the electronic waste containing gold, silver and palladium contains 0.01% gold, 0.05% palladium, and 0.08% silver; the extraction process is shown in Figure 1: 1 g of electronic waste containing gold, silver and palladium is discarded The powder was put into 30 mL of choline chloride-urea liquid solvent containing 1 mol/L cupric chloride (solid-to-liquid mass ratio was 1:30 g/mL), heated in a water bath, and the temperature was 90 °C. Leach for 10min, filter after leaching, add 30mL of deionized water to the first filtrate, the gold ions in the first filtrate are reduced to gold element for precipitation, while the silver ions in the filtrate are reduced to silver chloride for precipitation, and then Add 10ml of 0.5mol/L calcium chloride solution, the silver chloride will dissolve in the solution at this time, filter out the gold element at this time, and filter to obtain the second filtrate and gold element; then add 30mL to the second filtrate The silver ions were reduced by deionized water, and the silver chloride was filtered out to obtain the third filtrate and silver chloride; 18 mL of 0.1 mol/L butanedione oxime ethanol solution was added to the third filtrate, and the filtrate was The palladium ions in the dimethylglyoxime palladium are precipitated. Filtration gave the fourth filtrate and palladium dimethylglyoxime. Finally, elemental gold, silver chloride and palladium dimethylglyoxime were obtained from the precipitate. Among them, the leaching rate of gold is over 99.6%, that of silver is over 99.5%, and that of palladium is over 99.4%. Electron microscopy was performed on the precipitated gold, the precipitated silver chloride, and the precipitated dimethylglyoxime palladium, respectively. Through energy spectrum analysis, we found that in the detection of the precipitates, we did not find the peaks of other metals, showing a class of ions. High-purity selective recovery of gold-silver-palladium from electronic waste powders containing gold-silver-palladium by a liquid-chloride system.

Example 3

After digestion, the electronic waste containing gold, silver and palladium contains 0.02% gold, 0.08% palladium and 0.08% silver; the extraction process is shown in Figure 1: 3g of electronic waste containing gold, silver and palladium is discarded The powder was put into 30 mL of choline chloride-urea liquid solvent containing 1.2 mol/L copper chloride (solid-liquid mass ratio was 1:10 g/mL), heated in a water bath, and the temperature was 90 °C. Leach for 10min, filter after leaching, add 30mL of deionized water to the first filtrate, the gold ions in the first filtrate are reduced to gold element for precipitation, while the silver ions in the filtrate are reduced to silver chloride for precipitation, and then Add 10ml of 0.5mol/L calcium chloride solution, the silver chloride will dissolve in the solution at this time, filter out the gold element at this time, and filter to obtain the second filtrate and gold element; then add 30mL to the second filtrate The silver ions were reduced by deionized water, and the silver chloride was filtered out to obtain the third filtrate and silver chloride; 18 mL of 0.1 mol/L butanedione oxime ethanol solution was added to the third filtrate, and the filtrate was The palladium ions in the dimethylglyoxime palladium are precipitated. Filtration gave the fourth filtrate and palladium dimethylglyoxime. Finally, elemental gold, silver chloride and palladium dimethylglyoxime were obtained from the precipitate. Among them, the leaching rate of gold is over 99.5%, that of silver is over 99.6%, and that of palladium is over 99.99%. Electron microscopy was performed on the precipitated gold, the precipitated silver chloride, and the precipitated dimethylglyoxime palladium, respectively. Through energy spectrum analysis, we found that in the detection of the precipitates, we did not find the peaks of other metals, showing a class of ions. High-purity selective recovery of gold-silver-palladium from electronic waste powders containing gold-silver-palladium by a liquid-chloride system.

Claims (7)

1. A method for selectively leaching and recovering precious metal gold, silver and palladium in electronic waste is characterized by comprising the following specific steps: (1) taking a mixed solution composed of inorganic chloride and an ionic liquid-like solvent as a leaching solution, adding electronic waste powder containing gold, silver and palladium into the leaching solution according to a solid-liquid mass-volume ratio of 1:10-1:90g/mL for leaching reaction, wherein the leaching temperature is 30-90 ℃, the leaching time is 10-60min, and after leaching is finished, filtering to obtain a first filtrate and filter residue;

(2) adding deionized water into the first filtrate to reduce and precipitate gold ions and silver ions in the filtrate, filtering after precipitation to obtain a silver-gold mixture and a second filtrate, adding a calcium chloride solution with a certain concentration into the gold-silver mixed precipitate to dissolve the precipitated silver chloride, and filtering to obtain a fourth filtrate and a gold simple substance;

(3) adding dimethylglyoxime ethanol solution into the second filtrate to precipitate palladium ions, and filtering to obtain a third filtrate and dimethylglyoxime palladium;

(4) adding deionized water into the fourth filtrate to precipitate silver, and filtering after reduction to obtain silver chloride precipitate and a fifth filtrate; the above steps are respectively implemented to recover the simple substance, the silver chloride and the palladium dimethylglyoxime;

(5) the third filtrate can be used for leaching again after rotary evaporation, and closed cycle is realized.

2. The method according to claim 1, wherein in the step (1), the solid-liquid mass volume ratio of the mixed solution of the gold-silver-palladium-containing electronic waste powder, the inorganic chloride and the ionic liquid-like solvent is 1:10-1:40 g/mL; the leaching temperature is 80-90 deg.C, and the leaching time is 10-20 min.

3. The method according to claim 1, wherein in the step (1), the inorganic chloride salt is one or more of copper chloride dihydrate, anhydrous copper chloride and ferric chloride; the concentration of the inorganic chloride salt in the mixed solution is as follows: 0.25-1.5 mol/L; the ionic liquid-like 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 mol ratio of the choline chloride to the other component is as follows: 1:2.

4. The method according to claim 1, wherein in the step (2), the calcium chloride solution is added in an amount of 20 to 80% by volume of the leachate at a concentration of 0.5 to 1 mol/L.

5. The method of claim 1, wherein the volume ratio of deionized water to the first filtrate in step (2) is: 1: 2-2: 1, the precipitation time is 0.5-1.5 h.

6. The method according to claim 1, wherein in the step (3), 1mol/L to 1mol/L of the dimethylglyoxime ethanol solution is added to the second filtrate to precipitate and reduce the palladium, and the dimethylglyoxime ethanol solution is added in an amount of 40 to 100 percent by volume of the leachate.

7. The method according to claim 1, wherein in the step (4), the deionized water is added to the fourth filtrate in an amount equal to the volume of the leachate.

Images