A method of processing material based on carbon containing precious metal

 

(57) Abstract:

The present invention relates to technology of precious metals, mainly silver, palladium, platinum, and can be used for removal of carbon materials, including carbon catalysts, sorbents, organic residues. Carry out thermal treatment of the material in the presence of an oxidant, which is used as the alkali metal sulfate at a ratio of C: SO4-2= 1: 1.5 to 2.5, at a temperature of 900-1100C for 0.5 to 2.0 hours with the formation of addition of the alkali metal sulfide, leached with water transfer of the formed sulfide in solution, and separating the precipitate containing a noble metal. The proposed method allows to increase the degree of extraction of the precious metal to 97.5 99.8 per cent and to obtain additional product: lithium sulfide, sodium or potassium, depending on the type of oxidant used in the process. In addition, when implementing the method, the carbon substrate is used to obtain sulfide product. 3 C.p. f-crystals.

The present invention relates to technology of precious metals, mainly silver, palladium, platinum, and can be used for WPI is tcov.

Platinum, palladium, silver is usually applied to the substrate of the catalyst, which use coal, organic matter or other material. The metal is on the surface of the medium in small amounts (0.05 to about 1-2 wt.%). Coal is a highly efficient reagent for the sorption of silver and other precious metals and is widely used for the purification of solutions containing precious metals. Organic silver-containing materials are photographic film, photographic paper, electronic printed circuit boards. In the course of the reaction the catalyst adsorbs the components of the reaction mass and lose their activity. So after a few cycles raises the question of regeneration or recycling of the catalyst. However, existing methods of disposal of materials based on carbon, containing precious metals, macoeconomic and do not provide complete use of all components, including the substrate material.

There is a method of processing material based on carbon containing a noble metal, in particular palladium (see German patent N 2659391, MKI2C 22 B 11/02, 1977), by processing spent palladium catalyst or polucheniya palladium then degraded by acids.

The disadvantages of the method are the need to work with gaseous fluorine, the complexity of hardware design and high security requirements of the process.

There is a method of processing material based on carbon containing a noble metal, in particular silver or platinum group metal (see German patent N 2508906, MKI2C 22 B, 1975), by treatment for 4 hours aqueous suspension of the material at a temperature of 200oC and a pressure of 75 ATM. in the atmosphere containing oxygen in a quantity sufficient to oxidize all of the carbon.

The disadvantages of this method are the relatively low recovery of precious metal, for example palladium (96.7%), the need for the use of pressure equipment and the duration of the process.

Also known is a method of processing material based on carbon containing a noble metal, in particular palladium (see author's certificate Czechoslovakia, N 181439, MKI301 J 23/44, 1980), according to which the palladium catalyst is burned in air, while the oxidizer is present in him oxygen, the ash after combustion catalyst leached with hydrochloric acid and separated by filtering rest the Oia is mixed with the spent catalyst and the mixture is burned. The resulting ash is re-leached with hydrochloric acid. The degree of extraction of palladium is 96-97%.

The disadvantages of this method are not sufficiently high recovery of palladium, the loss of the substrate material by burning, and the significant length of the process, due to the fact that the rate of burning is a few percent per hour.

The present invention is directed to solving the problem of increasing the degree of extraction of the precious metal in concentrate and more sulfide product using the substrate material.

The problem is solved in that in the method of processing material based on carbon containing a noble metal, including heat treatment of the material in the presence of an oxidising agent and a noble metal from the products of thermal treatment, according to the invention as oxidant used solfataras reagent at a ratio of C : SO4-2= 1:1.5-2.5, and heat treatment is carried out at a temperature of 900-1100oC obtaining additional sulfide-bearing product.

The problem is solved also by the fact that as selfaddressed reagent ISA task aims what heat treatment is carried out for 0.5 to 2.0 hours.

The solution of this problem is achieved by the fact that sulfide-bearing product is a sulfide of an alkali metal.

The essence of the present invention is that the materials based on carbon containing precious metals are used to produce sulfides of alkali metals. This ensures the recovery of precious metals and recycling carbon basis according to the reaction

2C+Me2SO4--->Me2S+2CO2, (1)

where Me is Li, Na, K

As the furnace atmosphere contains oxygen, the carbon is consumed in the following reaction

2C + O2= 2CO (2)

2CO + O2= 2CO2(3)

The process temperature should be maintained in the range of 900-1100oC. At temperatures below 900oC the rate of recovery of sulphate is low, because the recovery at these temperatures is mainly due to the action of carbon monoxide:

4CO + Me2SO4---> Me2S + 4CO2(4)

Only after the appearance of the liquid phase (melting point of Li2SO4- 859oC, Na2SO4- 890oC, K2SO4- 1069oC) wetting powerhose temperature above 1100oC is impractical because the gains from further increase the speed of the process does not compensate for the energy cost of heating system. After melting of sulfate observed "boiling" water, caused by the rapid release of gases, however, as the sulphide formation and growth of its content, the melt thickens.

In accordance with reaction (1) consumption of carbon should be about 25% of the weight of SO4-2but because the process is accompanied by the burning of carbon in reactions (2) and (3) its consumption is significantly higher than calculated by equation (1). The process when the ratio of C : SO4-2more than 1:1.5 leads to the fact that some of the carbon remains unreacted and, ultimately, lead to a poorer concentrate of precious metals. When working in the interval for the ratio of C: SO4-2= 1:1.5-2.5 in the formed water is a certain amount of sulfate that allows you to maintain the melt in a sufficiently fluid state at temperatures below the melting temperature of the corresponding sulfides. The number of unrecovered sulfate should be greater, the lower the temperature in the furnace. If, for example, to recover all of the sodium sulfate, the pace of the process when the ratio of C:SO4-2less than 1:2.5 leads to excess reagent. In the floating remains of a large excess of sulfate, which contaminates the resulting sulfide.

The duration of the recovery process is in the range of 0.5-2.0 hours, depending on the size of particles of carbonaceous material and the process temperature. Increase recovery time of over 2 hours is impractical because it is not practically possible to increase the degree of conversion of material and recovery of metals, and with a duration less than 0.5 hours, the reaction does not have time to go in full.

After cooling and solidification of the melt it is crushed and sent for leaching. In addition to the impurities formed as a result of adverse reactions, the melt may contain the residue of unreacted carbonaceous material and ash from its combustion. Leaching is carried out with water at a temperature of 80-100oC with constant stirring.

After the smelt dissolving in water, the resulting solution is separated from the insoluble precipitate. Solution containing at a temperature of 80-100oC up to 30-35% of the alkali metal sulfide, and sulfide is the product. Sulfides can be obtained in the form of solutions or after upark the material, concentrated up to 99.8% of the noble metal. The main source of loss of material is an alkaline solution of sulfide, in which the formation of soluble tizaidine. However, during the transition from potassium to lithium metal loss solution decreases. This is probably due to the lower solubility of lithium in solutions with low alkalinity. The resulting concentrate contains up to 15.2% of recoverable precious metal.

The nature and advantages of the proposed method can be explained by the following examples.

Example 1. In a pot load of 20 g of the catalyst containing 1.27% Pd, add 60 g of sodium sulfate (C:SO4-2= 1:2.0), and the mixture is stirred. The crucible is set in the oven and turn up the heat, the heating rate of the order of 10oC/min. Temperature holding process 1000oC. After the regime maintain the melt at a given temperature for 1 hour and remove the crucible from the furnace. The melt is ground, add water to ensure that the ratio of T : W of 1 : 3 and maintaining the temperature within the 100oC, leached water. Sulfide product in the form of sodium sulfide when it goes into solution, from which it is separated by filtration from the insoluble precipitate. OS the Oia 97.9%.

Example 2. The process is conducted according to Example 1 except that the melt is maintained at 900oC for 1 hour. Get the sodium sulfide solution and palladium precipitate. The weight of sediment 2.193 g, the palladium content of 11.4%, the degree of recovery of 98.1%.

Example 3. The process is conducted according to Example 1, but take 20 g of the catalyst containing 1.27% Pd add 45 g of sodium sulfate (C:SO4-2= 1:1.5) and the melt is maintained at 1100oC for 1 hour. Get the sodium sulfide solution and palladium precipitate. The weight of sediment 1.396 g, the content of palladium 8.93%, the degree of recovery of 98.2%.

Example 4. The process is conducted according to Example 1, but as the oxidant used potassium sulfate. Take 20 g of the catalyst containing 1.27% Pd, add 70 g of potassium sulfate (C:SO4-2= 1:1.9), and the melt is maintained at 1100oC for 1 hour. Get solution of sulphide of potassium and palladium precipitate. The weight of sediment 1.627 g, the content of palladium 15.23%, the degree of recovery of 97.5%.

Example 5. The process is conducted according to Example 1, but as oxidant lithium sulfate is used. Take 10 g of catalyst containing 1.27% Pd add 28 grams of lithium sulfate (C:SO4-2= 1:2.5) and the melt is maintained at 1050oC adiya 9.16%, the degree of recovery of 99.0%.

Example 6. The process is conducted according to Example 5, the difference lies in the fact that take 10 g of catalyst containing 0.53% Pd, add 20 g of lithium sulfate (C: SO4-2= 1: 1.75), and the melt is maintained at 1050oC for 0.5 hours. Get solution of lithium sulfide and palladium precipitate. The weight of sediment 0.559 g, the palladium content 9.4%, the degree of recovery of 98.7%.

Example 7. The process is conducted according to Example 1, the difference lies in the fact that take 10 g of catalyst containing 0.53% Pd, add 25 g of sodium sulfate (C: SO4-2= 1:1.70) and the melt is maintained at 1050oC for 2 hours. Get the sodium sulfide solution and palladium precipitate. The weight of sediment 1.053 g, the content of palladium 4.99%, the degree of recovery of 99.2%.

Example 8. The process is conducted according to Example 1, the difference lies in the fact that taking 20 grams of coal sorbent containing 0.18% silver, and add 60 g of sodium sulfate. The temperature of the process 1050oC, the dwell time of the melt - 2 hours. Get solution of sodium sulfide and silver-containing precipitate. The weight of sediment 2.1 g, the silver content of 2.38%, the degree of recovery of 99.8 per cent.

Example 9. The process is conducted according to Example 1, the difference lies in the fact that they take 100 g whoa the process 1100oWith, the dwell time of the melt 2 hours. Get solution of sodium sulfide and platinochloride sediment. The weight of sediment 8.07 g, the content of platinum 11.7%, the degree of recovery of 98.4 per cent.

Thus, from these Examples it follows that the proposed method allows to increase the degree of extraction of the precious metal to 97.5-99.8% and get additional product: lithium sulfide, sodium or potassium, depending on the type of oxidant used in the process. Additionally, when implementing the method, the carbon substrate is used to obtain sulfide product.

1. A method of processing material based on carbon containing a noble metal, including heat treatment of the material in the presence of an oxidising agent and a noble metal from the products of thermal processing, characterized in that as the oxidant used solfataras reagent at a ratio of S : SO4-2= 1 : 1.5 to 2.5, and heat treatment is carried out at a temperature of 900 - 1100oC obtaining additional sulfide-bearing product.

2. The method according to p. 1, characterized in that as selfaddressed reagent use a sulfate of an alkali metal.

3. The method according to p. 1 or 2, oecause fact, that sulfide-bearing product is a sulfide of an alkali metal.

 

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