RU2066698C1 - Method of recovering gold and silver from waste of electronic and electrotechnical industry branches - Google Patents

Abstract

FIELD: recovery of gold and silver from electronic boards, electronic instrument scrap materials, waste of radiotechnical, electronic and timepiece industry branches. SUBSTANCE: method comprises of treating by nitric acid at temperature 50-70 C electronic boards and scrap material of electronic instruments; disintegrating waste and processing it by nitric acid whose concentration has been taken up to initial one at 90 C over two hours and then at boiling temperature. EFFECT: enhanced efficiency of process. 1 cl

Description

 The invention relates to the field of hydrometallurgy and can be used to extract gold and silver from electronic circuit boards of used electronic machines such as Minsk-32, EC-1035 and SM-1420, scrap and waste from the electronic, radio-technical and watch industries.

Known pyrometallurgical method for the extraction of gold, silver and platinoids from scrap electrical appliances, sludge from removing gilding, from the ashes from the burning of film and spent catalysts. This method involves grinding the material, crumpling it into pellets and then melting it in a shaft furnace with the addition of jet and coke, using limestone, quartz sand, iron oxide, pyrite, copper-containing slag, and matte as flux. After slag removal, lead is obtained with a total content of gold, silver and platinoids of 9 15%. According to this scheme, a plant was built in Austria by Comption Lyon Allmond Lonjot, which annually receives 3 tons of gold, 70 tons of silver, 250 kg of platinum and 300 kg of palladium from recycled materials ["EI" TsNIItsvetmet, ser. Secondary metallurgy of non-ferrous metals, 1983, N 5]
The disadvantage of this method is the ingress into the crushed product of a crushed plastic substrate / base / for fastening electronic parts in an amount up to 60% of the processed mixture and when melted which harmful gas emissions are emitted into the air that are difficult to clean and therefore polluting the air with phenols, dioxins and other toxins.

There is also known a method of leaching a layer of electronic scrap with a mixture of nitric and hydrochloric acids / "aqua regia" /. The method involves the dissolution of gold by percolation of acids through a layer of electronic scrap in a percolator with a false bottom, which is more efficient than mixing in the reactor [Japan, patent N 56-191054 from 01/28/81]
Closer to the proposed method is a hydrometallurgical method for leaching scrap electronic devices with nitric acid. According to this method, scrap is leached with 30-60% nitric acid with stirring for a duration sufficient to achieve a copper concentration of 150 g / L in the solution. After that, particles of plastic are separated from the obtained pulp, the pulp freed from plastic is treated with sulfuric acid, bringing its concentration to 40%, nitrogen oxides are distilled off, adsorbing them in a special column. In this case, copper sulfates crystallize, gold and tin acid are precipitated. Then, the solution is separated from the obtained pulp and silver and platinoids are extracted from it by cementing them with copper, and the washed precipitate is subjected to smelting, resulting in the production of gold kings [GDR, patent N 253048 from 01.10.86. VEB Bergbau und Huffen Kombinat "Albert Funk"]
Closest to the alleged invention is a hydrometallurgical method for leaching scrap electronic devices with nitric acid or a mixture of nitric acid with hydrochloric acid.

The disadvantages of this method are
an excessively large mass of crushed scrap subjected to nitric acid treatment due to its two to three-fold increase due to co-grinding of the plastic substrate on which electronic parts are attached, since manual separation of them requires a lot of labor,
exorbitantly high consumption of chemicals associated with the need to treat acids with an increased mass of crushed scrap,
low content of gold and silver with high concentrations of associated impurities in the sediments subjected to refining,
the release of toxins into the air and their infection of the air due to the release of toxins during the chemical destruction of plastics with strong acid solutions at elevated temperatures.

 These drawbacks are eliminated by the fact that the extraction of gold and silver from electronic circuit boards, scrap electronic devices, waste from the radio and watch industry, including grinding plastic boards, treatment with nitric acid, nitrogen oxide distillation, precipitation and reprecipitation of precious metals, calcining and smelting the precipitates to obtain precious metal ingots, and treatment with nitric acid is carried out initially at a temperature of 50 to 70 degrees. Celsius, after which the electronic parts are crushed and treated with acid reinforced at 90 degrees. Celsius for 2 hours, then at boiling point until the solution is completely denitrated.

 Example 1

 In a bathtub filled with a 30% solution of nitric acid with a temperature of 40–70 degrees. Celsius, immerse the plastic plateau with electronic parts and keep them in solution with periodic shaking until the electronic parts completely fall off from the circuit board. This is achieved with a specific flow rate of a 30% solution of nitric acid 0.20 0.22 l / plateau for up to 10 hours. In an equilibrium solution, at the time of the electronic component blade, 5 mg / l of gold, 46 mg / l of silver and 54.4 g / l of copper are contained.

 The plateaus freed from electronic parts after washing are sent to the scrap, and the electronic parts are ground.

 During the experiment, a 30% solution of nitric acid in the amount of 200 ml was prepared, it was heated, for example, to 60 deg. Celsius, was poured into an acid-resistant cuvette, similar in shape to a plateau, and a plateau with spent electronic parts was placed in it, the plateau was periodically shaken (2 3 times per hour), and after the electrical components fell off, the released plateau was removed from the cell. The solution was poured into a glass, the washed parts were crushed in a mill. The spent solution was brought to a volume of 500 ml, nitric acid was strengthened to 30%, the crushed parts were placed in it and heated for 2 hours at a temperature of 90 degrees. Celsius, was introduced 50 ml of concentrated sulfuric acid and boiled for 3 4 hours for its complete denitration.

In total, 9 plastic boards with electronic parts from the Minsk-32 computer and one electronic plateau with the EC-1035 and SM-1420 computers were processed. After chemical preparation, 426 g of circuit boards freed from electronic parts and 400 g of electronic parts were obtained (Table 1). After grinding to a particle size of 94% in the 0.2 mm class, the crushed mass was averaged and analyzed. The content in the crushed product was: gold 0.4 g / kg, silver
0.13 g / kg and copper 6.1%. During grinding, metal wool was formed, the yield of which by weight was 1% of the weight of the ground electronic parts. The content of gold was 9.4 g / kg, silver 0.4 g / kg and copper 40.3 g / l (Table 2).

 The effectiveness of the preparation effect was tested on electronic computers of other brands (Table 3), namely on the EU-1035 and SM-1420. The data obtained indicate the same effectiveness of the chemical preparation of the electronic circuit boards of these machines in comparison with the electronic plateau of the Minsk-32 computer.

 The crushed electronic plateaus were subjected to sequential treatment with nitric acid prepared from the spent preparation solution for 3–4 hours in an amount of 500 ml of 30% acid per 100 g of crushed material, denitration by sequential introduction of sulfuric or hydrochloric acid when heated to a temperature of 80–100 degrees . Celsius and the capture of nitrogen oxides in a special standard column. In the solution after treatment with nitric acid, copper was found to be 91 g / l, gold 600 1000 mg / l and silver 1 mg / l.

The denitrated solution, together with the fine slurries of silver chloride, is poured from the crushed leached product, which was washed 3-4 times with the settled solution to reduce losses and 40 ml of a 10% solution of hydrazine chloride were added in small portions while heating to 80 100 deg. Celsius. The solution was left to stand for 1 2 hours and filtered through a paper filter. The filter with the precipitate was washed with diluted 1: 100 hydrochloric or sulfuric acid, then with water and transferred to a porcelain crucible, the paper filter was dried in a sand bath and carefully milled in a muffle and then calcined at a temperature of 700 800 degrees. Celsius to obtain powdered gold with a purity of 76% and the presence of silver up to 10%. Melting the powder into ingots is not difficult when grinding in a crucible with 2 g of soda, 0.6 g of borax and 1 g of nitrate [Baryshnikov I.F. Sampling and analysis of precious metals. M. Metallurgizdat, 1978, p. 182 183]
From the mother liquor after precipitation of gold with hydrazine during evaporation, an aqueous salt of copper sulphide (vitriol) crystallized in an amount of 90-150 g / g of gold.

 Example 2

 In a bath filled with a mixture of nitric and hydrochloric acids in a 1: 3 ratio, plastic plates with electronic parts are immersed at room temperature and kept in solution with periodic shaking for one two hours until the electronic parts completely fall off from the plateau. This is achieved with a specific flow rate of the preparation solution of 0.133 l / plateau. In an equilibrium solution at the time of the roll-off of electronic parts, 21 mg / l of gold, 30 mg / l of silver and 75 g / l of copper are contained (Table 4).

 The introduction of hydrochloric acid into the preparation mixture in the ratio of 1 part of nitric acid and 3 parts of hydrochloric acid synergized the separation of electronic parts from a plastic plateau. As a result, the specific consumption of the preparation solution decreased from 0.22 l / plateau (nitric acid) to 0.132 l / plateau or 1.3 ml / g plateau or 2.2 2.4 ml / g of electronic parts (acid mixture) and reduced the duration of the roll-off of electronic parts from a plastic plateau from 10 to 1 2 hours. Using 15% hydrochloric acid as a preparation solution was less effective than treating a plateau with electronic parts with nitric acid. So, processing one plateau IY-1 2RB for up to 24 hours neither at room temperature nor during heating did not separate the electronic parts from the plastic plateau. The content of components in the equilibrium hydrochloric acid solution was 1.74 g / l for copper, less than 0.1 mg / l for gold and 5 mg / l for silver. This confirms the synergistic properties of the preparation solution when preparing it from a mixture of nitric and hydrochloric acids.

 Replacing hydrochloric acid with sulfuric acid worsened the separating properties of the preparation solution, and this solution was able to separate electronic parts from only one plateau N YIII-5 (specific consumption of the solution 1 l / plateau) at a concentration of 13.8 g / l of copper, gold 4 in the equilibrium solution , 7 mg / l and silver 27 mg / l.

 After chemical preparation, 15 plastic boards with a total weight of 756 g with an interval of oscillation of their weights from 42 to 102 g were freed from electronic parts and 656 g of electronic parts of various grades were obtained. The latter were crushed without preliminary sorting and subjected to further processing with a mixture of hydrochloric and nitric acid, prepared on the basis of the spent preparation solution.

 The crushed electronic parts were dissolved in a solution of a mixture of nitric and hydrochloric acids in a ratio of 1: 3, prepared on the basis of a spent preparation separator. For 100 g of crushed parts, 500 ml of a mixture of acids was taken (specific solution flow rate of 5 ml / g), while the specific yield of the used preparation separator was only 2.2 2.4 ml / g of electronic parts. Details were processed for 3 to 4 hours at boiling point. The resulting solution, two to three times by evaporation with hydrochloric acid, was transferred to hydrochloric acid with the addition of 50 ml of hydrochloric acid with a density of 1.05 g / ml each time. Then the solution was diluted and its volume was brought up to 1 L with water and filtered. Silver chloride was precipitated, which was processed into metallic silver by standard methods, and the solution was heated to a temperature of 80–90 degrees. Celsius. In a solution with a gold concentration of 0.5 to 1.0 g / l, 40 ml of 10% hydrazine hydrochloride (hydroquinone or another precipitant may be added) were added with stirring, gold was precipitated, and the solution was heated for 30 minutes at a temperature of 80–90 degrees. Celsius, defended for 1 2 hours and filtered through a paper ashless filter. The precipitate on a paper filter was washed with dilute hydrochloric acid (1: 100) and water, together with the filter it was transferred to a porcelain crucible, dried in a sand bath and carefully milled in a muffle, and then calcined at a temperature of 700,900 degrees. Celsius.

 The purity of the gold powder is 99.9%. When re-precipitating gold, its purity is increased to 99.99%. If it is necessary to obtain a gold ingot, the gold powder was smelted by known methods, for example, in the presence of 2 g of soda, 0.6 g of borax and 1 g per 1 g of gold g saltpeter.

Loss of gold in the processing of circuit boards is 0.04 mg / 100 g of electronic parts and are distributed as follows:
plastic plates exempted from electronic parts with a residual gold content of 0.2 g / ton 0.02 mg / 100 g plateau or 100 g electronic parts,
a precipitate of silver chloride with the remains of unbroken glass with a gold content of 0.3 g / t 0.01 mg / 100 g of electronic parts,
mother liquor after deposition with a gold content of 0.010 mg / l 0.01 mg / 100 g of electronic parts.

In the crushed electronic parts, the gold content was 400 g / kg or 40 g / 100 g of electronic parts. The technological extraction of gold is 99%. Taking into account production losses, a gap in the balance due to the accuracy of testing and analysis and other production factors, commodity extraction should be taken according to the new method in the amount of 97.3 98.4%
The commodity yield of silver for computers of the indicated classes is 300,400 g / kg of gold bullion.

From the mother liquor after precipitation of gold by hydrazine by evaporation, a concentrated solution of copper chloride of the following composition 3CuO • 2CuCl ₂ • 4H ₂ O was obtained in an amount of 90-150 g / g of gold.

Claims (1)

The method of extracting gold and silver from waste electronic and electrical industry, including grinding the starting material, treatment with a solution of nitric acid with a concentration of 30% dinitration with the capture of nitrogen oxides, precipitation and reprecipitation of noble metals from the resulting solution, calcining and smelting the precipitate to produce noble metals, characterized the fact that the treatment with a solution of nitric acid with a concentration of 30% is carried out at 50 70 ^o C until the separation of electronic parts, after separation of electronic parts containing gold and silver, is subjected to grinding and processing with a solution of nitric acid, strengthened after processing the starting material to the initial concentration, and processing at a temperature of 90 ^o C for 2 hours, and then at the boiling point of the solution until the solution is completely dinitrated to obtain a solution containing noble metals.

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