RU2017842C1 - Method of reprocessing of alloys containing noble metals on the basis of copper and/or zinc - Google Patents

Abstract

FIELD: reprocessing of metallic waste. SUBSTANCE: initial material containing more than 45% noble metals is dissolved in nitric acid. Noble metals are extracted from solution by cementing alloys. Alloy-cementer must have developed surface. EFFECT: improved method of noble metals extraction. 4 cl

Description

 The invention relates to hydrometallurgy and can be used at metallurgical and chemical enterprises for the processing of metal waste containing noble metals. The method allows to process waste with a noble metal content from 5 to 80%, reduce processing costs by eliminating expensive reagents and reduce material flows, improve the environmental situation in the processing process.

 The widespread use of precious metals in the national economy leads to the formation of a large amount of waste, very different both in physical condition and in the content of valuable components and impurities. Alloys of silver with copper, zinc and other non-ferrous metals, metal-based contacts, and bimetallic products containing gold and silver have received the greatest application in electrical engineering and electronics. When processing secondary silver- and gold-containing raw materials, industrial wastes and products that have undergone primary processing, most of the precious metals are extracted precisely from alloys.

 Known methods for processing this recycled material are not effective. Thus, the addition of silver, copper and silver-zinc alloys to copper smelting units and their processing in a full cycle of copper production technology cause large losses of precious metals.

A known method of processing copper-based alloys containing up to 40% silver. The method includes sulfuric acid leaching in the presence of hydrogen peroxide or sodium persulfate. The sulfuric acid concentration of 180-220 g / l, the ratio of W: T = 10: 1, temperature of 55 ^C. The duration of the leaching of copper is 3.5-4 hours at the initial alloy grain size less than 0.2 mm. As a result, 91-93% copper and 0.1-0.2% silver pass into the solution.

 A method has been developed for refining mixtures of alloys containing copper and silver, which consists in the fact that the specified finely ground mixture is treated with a solution of sulfuric acid while passing steam and air through it. The resulting copper sulfate is separated from the undissolved residue. The residue is refined by cathodic deposition, where the anode is pieces of refined alloy loaded, for example, into a perforated titanium drum. The electrolyte is a solution of sulfuric acid with the addition of sulfate or copper nitrate.

 These methods make it possible to selectively transfer copper into solution and mainly separate copper and silver. However, when leaching alloys containing more than 40-45% silver, the extraction of copper into the solution is significantly reduced with a sharp increase in the leaching time.

 A known method of processing alloys (silver-cadmium and silver-copper), based on their dissolution in nitric acid (1: 1). From the resulting solution, silver is isolated by known methods: electrolysis, cementation, precipitation of silver chloride. Using leaching in nitric acid, gold-based wastes can also be recycled on a metal basis.

 This combined method of processing silver-copper alloys has high productivity and allows you to process alloys of various contents. However, when dissolving alloys containing less than 45% silver, the consumption of nitric acid increases significantly. In addition, the separation of silver from a solution by electrolysis requires a large consumption of electricity. Precipitation of silver in the form of chloride is a faster and easier way, but subsequent melting of silver chloride is accompanied by increased losses of the noble metal. Cementing silver also allows the process to be carried out at a high speed; Smelting silver cement does not cause problems. However, the implementation of the cementation process requires the use of additional materials - often expensive, powders of copper, zinc, etc.

 The invention consists in dissolving the starting alloys in solutions containing nitric acid, followed by cementation of a new portion of the starting alloys; in this case, the initial alloys used for cementation are pre-crushed (cement-alloy should have a developed surface). Another condition for the implementation of the method is to maintain the difference between the silver content in the dissolved alloy and the cement-alloy. In this case, alloys with a silver content of more than 45% are subjected to dissolution, and the silver content in the cement-alloy should be either less than in the original alloy or more. In the first case, the product obtained is cement silver, and in the second, cement silver and enriched alloy. When the silver content in the enriched alloy is less than 80%, it is sent for dissolution, and when the content in the enriched alloy is more than 80% silver, the resulting product is an alloy of cement silver with an enriched cement-alloy.

 The technical result obtained by the implementation of this method is that it is possible to recycle waste containing noble metals in a wide range of concentrations - from 5 to 80%. The implementation of this method, while retaining the advantages of the cementation process over other methods for the separation of precious metals (electrolysis, salt deposition), can significantly reduce processing costs due to the fact that the process does not require the use of expensive metal-cementing agents and the consumption of nitric acid is reduced. In addition, the use of metals included in the feedstock as cementing agents leads to a decrease in the costs of the subsequent processing of waste solutions (non-ferrous metals) and a decrease in material flows in general. The introduction of hydrometallurgical technology for waste processing can reduce the amount of harmful emissions and improve the environmental situation in the workplace.

 It is most expedient to organize the processing of secondary raw materials in such a way that both rich raw materials and poor alloys are introduced. In this case, the product of processing will be silver cement. Granules enriched in the content of precious metals are sent for dissolution followed by cementation.

 When cementing with richer granules and obtaining enriched granules with a silver content of more than 80%, they are a processed product and are sent for refining.

 The method is as follows.

 Silver alloys of various compositions are ground, for example, granulated. Granules containing more than 45% silver and not more than 5% gold are dissolved in nitric acid. The resulting nitric acid solution is sent to cementation. Silver cementing is also carried out by granular metal waste of silver-containing alloys, using in the process other components that make up this alloy — copper, zinc, cadmium, etc., which are more electronegative metals than silver. Cementation is carried out with alloys containing less than 45% silver. Silver from the solution is precipitated in the form of a fine powder and mixed with the original granules. Silver-cement metals pass into solution. When carrying out the cementation process in an apparatus that does not allow cement silver to mix with the initial granules, for example, when loading granules into a mesh drum, three products are obtained: cement silver, granules enriched in silver, and a silver-free solution. Cement silver after washing and drying contains not less than 95% silver with the content of other metals not more than 4%. The initial low-grade granules containing up to 45% silver are enriched due to the transition of more electronegative metals into the solution by 30-40% and are sent for refining or dissolution followed by cementation.

 When using alloys with a silver content of more than 45% as a cementer, the problem of enrichment of the initial alloys is most fully solved. In this case, a mixture of silver cement with enriched granules containing more than 80% silver is obtained, and the alloy of this mixture is sent to refining.

 To implement the method, standard equipment can be used (reactors of various designs, melting units, screening, etc. The materials used, including acids, are relatively cheap and not scarce.

 PRI me R 1. 100 kg of waste copper-silver alloy containing 54% silver and 46% copper, dissolved in 400 l of a solution of nitric acid (1: 1). 360 l of the resulting solution with a silver content of 150 g / l and copper 128 g / l are directed to the allocation of silver by cementation. Cementation is carried out with granules of base alloy in an amount of 50 kg containing 35% silver, 60% copper, 5% of other impurities. The granule size is 3 mm. Cementation is carried out in a reactor with mechanical stirring for 4 hours. As a result, after drying, 85 kg of a mixture of silver cement with enriched granules are obtained. The silver content in the mixture is 83% and it is sent for melting to the anodes for subsequent electrolytic refining. Spent electrolyte is sent to the selection of non-ferrous metals.

 The extraction of silver in the cementation process is more than 98%.

 PRI me R 2. 100 kg of an alloy containing 62% silver, 10% copper, 25% zinc, 3% of other impurities, dissolved in 400 l of a solution of nitric acid. 380 l of the resulting solution with a silver content of 163 g / l, copper 26 g / l and zinc 66 g / l are sent to silver cementation. Cementation is carried out with granules of base alloy in an amount of 60 kg with a silver content of 28%, copper 21%, zinc 49%, other impurities 2%. The particle size of the alloy is + 2 - 6 mm. Cementation is carried out in a mesh drum immersed in a solution for 6 hours. As a result, after washing and drying, 64 kg of silver cement with a silver content of 50% are obtained; spent demineralized solution. Cement silver is sent for melting to the anodes, and enriched granules - for dissolution and subsequent cementation of silver.

 The extraction of silver in the cement is more than 98%.

 PRI me R 3. 50 kg of an alloy containing 58% silver, 0.5% gold, 32% copper, 7% zinc, 2.5% of other impurities, dissolved in 200 l of a solution of nitric acid. 190 l of the resulting solution with a silver content of 150 g / l is directed to cementation. Cementation is carried out with granules containing 70% silver, 0.8% gold, 25% copper, 3% zinc, 1.2% of other impurities. The number of granules is 30 kg, fineness is less than 1 mm. Cementation is carried out in a reactor with mechanical stirring for 2 hours. Cementate together with enriched granules is discharged onto a suction filter and washed with 150 l of deionized water. As a result, after drying, 44.6 kg of precipitate with a silver content of 96.4% and gold 1.1% are obtained. The precipitate is sent for melting to the anodes. The solution (together with wash water) containing 23 g / l of silver is sent to the final selection of silver and non-ferrous metals. The total recovery of silver is 97%, gold 99%.

 PRI me R 4. 100 kg of metal waste electrical production (contacts, substrates, etc.) with an average silver content of 49% is dissolved in 360 l of nitric acid. 350 l of the resulting solution with a silver content of 140 g / l is directed to cementation. Cementation is carried out for 2 hours with waste metal mesh made of copper-silver wire. The diameter of the wire is 0.1 mm, the silver content in it is 5%, the rest is copper. The cementate (after washing and drying) contains 94% silver and 3% copper - it is sent for melting to the anodes. The solution is directed to the selection of copper.

 Total silver recovery of at least 98%.

Claims (4)

 1. METHOD FOR PROCESSING ALLOYS CONTAINING NOBLE METALS BASED ON COPPER AND / OR ZINC, including dissolving in solutions containing nitric acid, and subsequent isolation of noble metals by cementation, characterized in that alloys with a noble metal content of more than 45% are dissolved, with cement content of more than 45% carried out by alloys either with a lower content of noble metals to obtain a noble metal cement, or with a higher content of noble metals with a noble metal cement and tse alloy a mentor enriched with precious metals, followed by the isolation of precious metals from the resulting products.  2. The method according to claim 1, characterized in that the cementation is carried out by an alloy with a developed surface.  3. The method according to PP. 1 and 2, characterized in that the developed surface is provided either by mechanical grinding or granulation.  4. The method according to claim 1, characterized in that when the content of noble metals in the enriched cement-alloy is less than 80%, noble metals are extracted by dissolving the alloy, and when the content of noble metals in the enriched cement-cement is more than 80%, noble metals by fusion with a noble metal cementer followed by electrolysis.