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INVENTION
Russian Federation Patent RU2164255

METHOD extracting precious metals from products containing silver chloride, PLATINUM GROUP METALS AND GOLD

METHOD extracting precious metals from products containing silver chloride, PLATINUM GROUP METALS AND GOLD

Name of the inventor: Sidorenko YA .; Efimov VN .; Moskalev AV .; Yeltsin SI
The name of the patentee: JSC "Krasnoyarsk Nonferrous Metals Plant"
Address for correspondence: 660027, Krasnoyarsk, transport fare 1, JSC "Krasnoyarsk Nonferrous Metals Plant", the science department
Starting date of the patent: 1999.02.04

The invention relates to metallurgy and noble metals can be used for the processing of products containing silver chloride, gold, platinum group metals, base elements advantageously insoluble residues pylevozgonov refining industries. The process comprises melting the starting material in the presence of a flux forming an alkali metal oxide, an alloy unit with predominant content of silver from the slag, the dissolution of the alloy in a nitric acid solution, precipitation of the nitrate solution of metal hydroxides - impurities at pH 2 - 5, reducing melt platinum group of undissolved residue alloy and hydroxides. The method reduces the costs of refining of the alloy, reduce the content of precious metals in the slag, to make a more complete cleaning of the silver nitrate solution of a platinum group metal impurities in the hydrolysis process.

DESCRIPTION OF THE INVENTION

The invention relates to metallurgy and noble metals can be used for producing silver and platinum group metals (PGM).

In the production of noble metal are inevitably formed various waste products and non-target containing well to ignoble basis, valuable components, including silver - as in the metal and in the chloride form. Among these products are dust and dust concentrate (PC), formed in the cleaning of dusty gases pyrometallurgical processing refinery production (dust concentrate called insoluble dust residue, the resulting washing ESPs).

A characteristic feature of these products is that their base is represented by a large number of various base elements and their compounds, the main of which are:

- Volatile components (selenium, tellurium, lead, bismuth, etc.);

- Chlorides of silver and base elements, resulting from the interaction of dust particles with chlorine or chlorine-containing compounds;

- Black carbon originating from the furnace off-gases resulting from the disproportionation reaction of CO at lower temperatures;

- Silica, and other water-insoluble oxides, which are the most typical components heat treatable batches.

It characterized by the following dust concentrate containing precious metals,%: Pt - 0,08-0,25; Pd - 0,15-0,35; Rh - 0,05-0,15; Ir - 0,03-0,1; Ru - 0,1-0,3; Au - 0,05 - 0,15; Ag - 5-15.

The method for extracting precious metals from dust concentrate the refining industry, which comprises: mixing starting KP 5-6 fold amount of magnesia powder, calcining the mixture at 350 o C, calcine leaching with hydrochloric acid, separation of the insoluble residue (nd) of the chloride solution , leaching of NO in ammonia water (with the transfer of silver in ammonia solution and concentrating the PGMs and gold nd ammonia leaching), concentrating melting nd Chloride solutions obtained by dissolving hydrochloric calcine was evaporated to dry salts, which are then calcined and used along with magnesia lining to be mixed with a new portion of the CS. [Patent RF N 2006508 on the application N 5027777 from 17.02.92, the "method of extracting precious metals from dust concentrate refining industry." Authors: EA Golubov, Gold AF]

The disadvantages of the method-analogue is the long duration of the technological cycle of recovery of valuable components due to the strong dilution of the original dust magnesite concentrate and extremely slow the reactions of solid-phase interaction contained in the concentrate dust chloride with magnesium oxide (when firing adopted temperatures), but also the high cost of evaporation chloride solutions and calcination of dry salt.

The closest in technical essence to the claimed method is the extraction of silver materials containing silver chloride impurities gold and platinum group metals. [Patent RF N 2096506 on the application N 96113774/02 from 07/05/96, the "method of extracting silver from materials containing silver chloride, gold impurity and platinum group metals." Authors: Loleyt SI Kalmykov YM, Ilchenko GA et al -. BI 1997, N 32, p. 281]. This method is taken as a prototype.

In the prototype method, the starting material is melted in a mixture with additives, forming an alkaline metal oxide to produce an alloy with a predominant content of silver separated alloy with a predominant content of silver slag and subjecting it to purification of impurities by blowing dry air melt in presence of soda ash, purified silver granulated and dissolved in nitric acid, separated nd solution of nitrate of the nitrate solution was precipitated hydroxides, hydroxides for use of them by hydrometallurgical PGM concentrate.

Disadvantages of the prototype method:

- The high cost of fire alloy refining with predominant content of silver;

- Transfer a significant part of noble metals in the slag in the melt blowing air;

- The lack of completeness of the cleaning solution of silver nitrate from PGM impurities in the hydrolysis process.

The proposed method makes it possible to obtain higher rates of extraction of precious metals in the desired products due to the exclusion of education for the rich precious metals refined slag and a full transition PGM and gold in the hydroxide precipitate.

This technical result is achieved by a method comprising melting a starting material comprising silver chloride, platinum group metals and gold, which is a mostly insoluble residue pylevozgonov refining industries, in the presence of a flux forming an alkali metal oxide, an alloy unit with predominant content of silver from the slag, silver dissolution in nitric acid solution, precipitation from nitric acid solution of silver metal hydroxide impurity of the invention dissolved in nitric acid is subjected directly to an alloy with a predominant content of silver, precipitation of hydroxides of metal impurities is carried out to a pH of from 2 to 5, the preparation of the platinum group metal concentrate from undissolved balance silver bullion and hydroxides is achieved by the smelting reduction. As a flux containing alkali metal oxides, the oxide slag using a sodium silicate and calcium, resulting in the production of the precious metals refinery, and product batch for melt containing silver chloride, has a composition, in weight.%:

Product containing silver chloride - 40 - 60

Calcium oxide - 5-15

Slag - Other

The method is based on a positive role base impurity elements, particularly such as iron, antimony, tin, tellurium, selenium alloy in the processes of dissolving silver content with a primary cleaning and hydrolytic impurities from the nitrate solution.

Said base element impurities (especially, antimony and tin) are formed in an alloy with silver content, acid predominant phase of platinum group metals. Upon dissolution of this alloy in nitric acid PGM concentrate predominantly insoluble residue. That portion of base elements impurities (mainly, iron, selenium, tellurium) which is moved from a nitrate solution alloy, serves as the collector (sorbent) that promotes fuller PGM coprecipitation hydroxides to precipitate during hydrolysis cleaning solution.

The optimal interval used the pH of the process of hydrolytic treatment chosen by experimentation. hardly occurs at pH less than 2 nitrate solution purification from impurities. When neutralizing the nitrate solution to pH = 2 the formation of significant amounts of precipitate hydroxides, preferably of antimony, tin, iron and tellurium and coprecipitation with them significant side IPY. Increasing the pH in the range from 2 to 5 facilitates continuous increase in extraction simultaneously precipitate hydroxides of iron, copper, selenium and platinum group metals. Increasing the pH above 5 is not desirable because it does not give a significant increase in MPG extracting precipitate hydroxides, but causes a strong increase in mass precipitate by switching it lead and silver, which results in reduced extract in citrate silver solution and complicates the process of preparation of noble metals .

The smelting reduction process hydroxides isolated during purification nitrate solutions with additives fluxes at 1200 - 1300 o C, noble elements partially distilled off in the gas phase, partially slags and IPY with impurities of gold and silver form rich in its content heavy alloy, which can be processed by known methods.

The use for the smelting reduction of the concentration of PGMs hydroxides is preferred (as compared to a non-reducing melting), as it provides higher recovery of precious metals in the heavy alloy target and improves the technological properties of the individual.

Since oxidic slags on the basis of sodium and calcium silicates formed in the refinery production, contain up to 70% of sodium and calcium silicates, the use of them in melting as a flux containing an alkali metal oxide, is a very promising and reduces production costs. The basis of using the slag refining industry as a flux on the ability of sodium silicate and calcium enter into reaction type (1) alkali-thermal reduction of silver chloride, it

2AgCl + 2Na 2 O · SiO 2 + CO = 2Ag + Na 2 O · 2SiO 2 + 2NaCl + CO 2 (1)

Terms alloy leaching process with predominant content of silver with nitric acid in the present process does not differ from those used in other similar processes. Silver extraction and purified from the resultant nitrate solution of PGM and may be carried out by known methods.

Examples of using.

Example 1. Taken 200 g (dry weight) of dust concentrate containing: 20.1% - silver chloride, 0.25% - platinum, 0.31% - palladium - 0.1% of rhodium, 0.08% - iridium 0.2% - ruthenium 0.09% - gold, 200 g of granulated slag through the oxide of sodium and calcium silicates formed in the refinery production, and 44.4 g of calcium oxide. All components were mixed batch was placed in a fireclay crucible, and subjected to laboratory melting in an electric furnace at a temperature of 1300 o C for 60 minutes.

As a result, 62.4 g of melting of the alloy obtained with a predominant content of silver containing 0.80% - platinum, 1.0% - palladium, 0.32% - rhodium, 0.25% - iridium 0.64% - ruthenium 0.29% - gold, 48.1% - silver, 1.0% - copper, 1.0% - iron, 16.0% - of lead, 1.0% - bismuth, 4.0% - selenium, 6 3% - tellurium, 5.3% - tin 9.5% - antimony.

When melting was obtained 249.0 g of slag containing 0.1% of silver, and not containing PGMs and gold (according to the spectral analysis).

The alloy with a predominant content of silver of silver bullion was divided into two equal parts, and one of them was subjected to processing according to the present method (see Example 1 cont.) And the other - according to the prototype method (see Example 2.).

Weigh obtained by melting an alloy with a predominant content of silver weighing 31.2 g was subjected to dissolve for two hours in a solution of nitric acid (64%, 14 M) at 80 o C, at T: L = 1: 1.2, with stirring the solution. The precipitate is separated by filtration from undissolved nitrate solution, the precipitate was washed with small amount of water from the washing solution attached to the main solution.

The result was obtained by 60 ml of nitric acid solution, which (according to ICP analysis) contained in g / L: Pt - 0,083; Pd - 1,30; Rh - 0,167; Ir - 0,467; Ru - 0,167; Au - 0,233; Ag - 241,3; Cu - 3,9; Fe - 0,4; Pb - 70,7; Bi - 4,2; Se - 12,5; Those - 13.1; Sn - 1,9.

The weight of undissolved residue (after drying) was obtained 12.1 g of n. about. contained,%: Pt - 2,0; Pd - 1,9; Rh - 0,74; Ir - 0,41; Ru - 1,57; Au - 0,62; Ag - 4,3; Cu - 0,64; Fe - 2,4; Pb - 6,2; Bi -0,5; Se - 4,1, Te - 9,8; Sn - 12,7.

The insoluble residue (nd) was used for the preparation of the charge for the processing smelting. To this end, 12.1 g nd was added 4.6 g of sodium carbonate and 1.7 g of coke fines, and the mixture was stirred, placed in a fireclay crucible, and subjected to melting in an electric furnace at a temperature of 1300 o C for 45 minutes.

As a result of melting obtained 5.09 g of the expected heavy alloy comprising (based on the spectral analysis): 4.8% - platinum, 4.5% - palladium, 1.8% - rhodium 1.0% - iridium 3 7% - ruthenium, 1.5% - gold, 10.2% - silver. The alloy of similar composition may be subjected to refining by known methods. When melting was obtained 7.2 g of slag not containing (based on spectral analysis) PGMs and gold.

Silver-nitrate solution was subjected to hydrolytic purification of metal impurities. To this end, 60 ml of the starting solution at 60 o C was added an alkaline solution (3N NaOH) until pH = 3,0. Consumption of caustic solution was 43 ml.

The precipitate of hydroxides from a solution which has passed most of the PGMs, about 85% iron, 10% copper and 11% lead, 7% bismuth and 40% selenium, and 90% of tellurium, 2.1% silver, filtered, dried and subjected to melting concentrating . To this end, 2.68 g of hydroxide sediment was added 1 g of sodium carbonate, 0.5 g of sodium silicate glass, 0.3 g of coke fines. The components were mixed batch was placed in an alundum crucible and subjected to melting in an electric furnace at a temperature of 1300 o C for 30 minutes.

The result obtained by melting 0.956 g of the expected heavy alloy containing 8.26% PGM and gold 31,3% silver, 31% Te, 10.4% Se, 15.6% lead and 2.1% copper. This alloy can be subjected to refining by known methods such as platinum metal concentrate. When melting was obtained 1.5 g of slag not containing PGMs, gold and silver.

As a third desired product which can then be directed to the deposition of silver using a variety of known techniques, obtained 100 ml of solution containing in g / l: Ag - 141,7; Pt - 0,022; Pd - 0,32; Rh - 0,052; Ir - 0,115; Ru - 0,053; Au - 0,095; Pb -37,7; Cu - 2,1; Se - 4,5; Te - 0,76; Fe - 0,04; Bi - 2,3; Sn - 1,0.

Thus, the direct extraction of silver nitrate solution of starting material - KP using the inventive method was 95.8% (based on the start nitrate dissolving 50% by weight obtained by melting an alloy with a predominant content of silver). Direct extraction of PGMs and gold (in total) to the target alloy from the original manual was 93.6%.

Example 2. Taken alloy with silver content advantageously obtained dust concentrate smelting (melting conditions see. Example 1). The alloy contains,%: platinum - 0.80; palladium - 1.0; rhodium - 0.32; iridium - 0.25; ruthenium - 0.64; gold - 0.29; Silver - 48.1; copper - 1.0; iron - 1.0; Lead - 16.0; Bismuth - 1.0; Selenium - 4.0; tellurium - 6.3; tin - 5.3; antimony - 9.5.

An alloy with a predominant content of silver in an amount of 31.2 g was placed in an alundum crucible, 20 g of soda ash was subjected to the refining and smelting in an electric furnace at 1150 o C. The resulting melt was subjected to purging with air for 30 minutes. After separation of the slag was obtained 18.6 g of silver-based alloy that has been subjected to granulation in an aqueous medium. The resulting silver-based granulate had the following composition,%: platinum - 1.02; Palladium - 1.18; rhodium - 0.43; Iridium - 0.38; ruthenium - 0.91; gold - 0.38; Silver - 68.8; copper - 1.3; iron - 0.09; Lead - 5.9; Bismuth - 0.7; Selenium - 4.8; tellurium - 6.9; tin - 1.6; Antimony - 2.2.

There was obtained 24.5 g of slag, which contained,% platinum - 0.24; Palladium - 0.37; rhodium - 0.08; iridium - 0.04; ruthenium - 0.12; gold - 0.08; Silver - 9.0.

The silver-based granulate (18.6 g) was dissolved over two hours in a solution of nitric acid (64%, 14M) at 80 o C, with stirring the solution. The precipitate is separated by filtration from undissolved nitrate solution, the precipitate is washed with water from the washing solution attached to the main solution.

The result was obtained by 50 ml of nitric acid solution, which (according to ICP) contained in g / L: Pt - 0,16; Pd - 1,76; Rh - 0,2; Ir - 0,4; Ru - 0,28; Au - 0,24; Ag - 248,2; Cu - 3,7; Fe - 0,02; Pb - 18,4; Bi - 1,8; Se - 10,8; Te - 10,2; Sn - 0,6; Sb - 0,8.

The weight of undissolved residue (after drying) was obtained 6.1 g of n. about. contained,%: Pt - 3,0; Pd - 2,2; Rh - 1,1; Ir - 0,8; Ru - 2,5; Au - 0,95; Ag - 6,3; Cu - 1,0; Fe - 0,2; Pb - 3,0; Bi-0,5; Se - 5,8; Te - 12,6; Sn - 4,4; Sb - 5,9.

Silver-nitrate solution was subjected to hydrolytic purification of metal impurities. To this end, 50 ml of the starting solution at 60 o C was added an alkaline solution (3N NaOH) until pH = 5,0. Alkali consumption was 40 ml.

After filtering the slurry and drying the precipitate obtained 1.85 g of metal hydroxide sludge, impurities, containing,%: Pt - 0,27; Pd - 2,65; Rh - 0,26; Ir - 0,54; Ru - 0,29; Au - 0,18; Ag - 13,5. By way of this prototype is processed pellet hydrometallurgical methods to obtain a concentrate of platinum group metals.

In 86 ml of a solution containing in g / l is obtained as a third title product: Ag - 141,4; Pt - 0,035; Pd - 0,45; Rh - 0,06; Ir-0,12; Ru - 0,10; Au - 0,10. The solution according to the prototype method is electrolyzed to produce refined silver.

Thus, according to prototype method in the direct recovery of silver nitrate solution of a starting alloy with a predominant content of silver bullion silver obtained by melting dust concentrate was 81.1%. Direct extraction of PGMs and gold alloy with a predominant content of silver in the insoluble residue from nitric dissolution of the granular silver alloy and metal hydroxides precipitate impurities (total) was 70.1%, significantly lower than when using the inventive method (95, 8% and 93.6% respectively).

CLAIM

1. A method of extracting precious metals from products containing silver chloride, platinum group metals and gold, preferably a water-insoluble residue pylevozgonov refining industries, comprising melting a starting material in the presence of a flux forming an alkali metal oxide, an alloy with a predominant content of the separation of silver from the slag dissolving silver in nitric acid solution, precipitation of the nitric acid solution of silver metal hydroxides impurities getting PGM concentrate of metal hydroxides impurities, characterized in that the dissolution in nitric acid is subjected directly to an alloy with a predominant content of silver precipitation of metal hydroxides impurities is carried out until a pH 2 - 5, the preparation of the PGM concentrate the undissolved residue and hydroxides of silver bullion is effected by smelting reduction.

2. A method according to claim 1, characterized in that a flux containing alkali metal oxides, the oxide slag using a sodium silicate and calcium, resulting in the production of the precious metals refinery, and product batch for melt containing silver chloride, has the following composition, wt.%:

Product containing silver chloride - 40 - 60

Calcium oxide - 5 - 15

Slag - Other

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Publication date 14.03.2007gg