RU2271399C1 - Method of leaching palladium from sludges - Google Patents

Abstract

FIELD: methods of treatment of circulating products containing palladium in form of metallic, oxide and metal-oxide forms.

SUBSTANCE: proposed method is used for production of stable isotopes in treatment of entrapping chambers of magnetic separators; metallurgy; processing ores and concentrates containing oxidized and native palladium and utilization of palladium-containing catalysts, as well as in analytical and preparative chemistry. Leaching is performed by solutions of nitric acid in presence of ammonium nitrate and weakly-basic anionite of epoxy-polyamine, type AH-31 at concentration of nitric acid in leaching solution from 120 to 190 g/l and ammonium nitrate from 160 to 240 g/l followed by separation of resin from pulp, washing of anionite with water from mother liquor and desorption of palladium from anionite. Proposed method increases degree of leaching palladium from sludge during one stage; method ensures obtaining pure solutions of palladium during its desorption from anionite reducing number of operations in treating the solutions for obtaining palladium or its compounds reducing the time required for conversion of palladium.

EFFECT: enhanced efficiency.

4 cl, 4 tbl, 4 ex

Description

The method of leaching palladium from sludges relates to the field of processing recycled products containing palladium in the form of metal, oxide and metal oxide forms, and can be used in the production of stable isotopes in the processing of nodes for collecting magnetic separators and in the metallurgy of palladium in the processing of ores and concentrates, containing oxidized and native palladium, and in the technology of utilization of palladium-containing catalysts, as well as in analytical and preparative chemistry.

The known method [RU 2211251 C2 (IPC C 22 V 11/00), publ. August 27, 2003] the extraction of platinum group metals, including palladium in the form of metal, oxide and metal-oxide forms, from anode sludges formed during the electrorefining of copper. The method includes dissolving the sludge in nitric acid, potentiostatic electrolysis on a porous electrode made of carbon material, and concentration of the remaining metal in solution on a solid extractant with returning the reextract to the electrolytic metal evolution cycle. This method provides, using nitric acid, a high degree of leaching of palladium from the anode sludge of copper electrorefining, completeness of the subsequent extraction of metal ions from the obtained leaching solutions, and a high degree of separation of palladium and impurities.

The disadvantage of this method - the prototype - is that the acid leaching method does not provide full opening of palladium of a large number of oxidized sludge, which leads to the loss of a valuable product. The completeness of opening of palladium-containing products is especially important in the technology for the production of stable isotopes, since the loss of even a small amount of isotopically enriched material leads to a significant decrease in the economic efficiency of the technology due to the high cost of the isotope separation process. In addition, this method does not provide selective leaching of platinum group metals. Therefore, in order to extract palladium, it is necessary to carry out additional operations of preparing and processing the obtained solutions, and this leads to an increase in the consumption of reagents and the number of operations, since any leaching process, as a rule, is associated with subsequent filtering operations, washing the precipitate from the mother liquor. This leads not only to hardware complication of the process and an increase in the duration of the cycle, but also to dilution of solutions and loss of the target component.

An object of the invention is to eliminate these disadvantages and to provide a significant increase in the degree of leaching of palladium from sludge in one stage. Obtaining pure solutions of palladium during its desorption from anion exchange resin, reducing the number of operations of the subsequent technology for processing solutions to obtain palladium or its compounds will reduce the consumption of reagents, the number of pieces of equipment and reduce the working time for servicing the redistribution of palladium.

The technical result is achieved by leaching palladium from sludges containing palladium in the form of metal, oxide and metal oxide forms with nitric acid solutions, while leaching of palladium is carried out with nitric acid solutions (120-190 g / l) with the addition of ammonium nitrate (160-240 g / l) in the presence of a weakly basic epoxy polyamine type of anion exchange resin AN-31, followed by separation of the anion exchange resin from the pulp, washing it with water and desorption of palladium from the anion exchange resin with ammonia.

The choice of concentrations of reagents in the solution and anion exchange resin for the sorption leaching of palladium is due to the fact that under these conditions not only a high degree of palladium recovery from sludges is provided (more than 99%), but it also separates from impurities of iron, copper, zinc, nickel, and titanium , chromium, manganese, gold, silver, etc. When using sorption leaching of palladium, a number of so-called persistent sludges are opened, of which palladium was practically not leached with nitric acid solutions, proposed by the known method.

A comparison of the effectiveness of the proposed and previously known method of the prototype is given in the examples.

Example 1. Leaching of palladium was performed from sludge with an average palladium content of 1%. The experiment was carried out under the following conditions. A sample of sludge, crushed to a particle size of less than 0.1 mm, in an amount of 5 g was poured into 100 ml of a solution with a certain concentration of reagents. In parallel, a similar experiment was conducted on the leaching of palladium in the presence of anionite AN-31, which was introduced into the prepared solution. For leaching, a resin fraction with a grain size of more than 0.5 mm was used, which ensured subsequent easy separation of the resin from the pulp. Leaching was carried out with constant stirring with air for 24 hours. This mixing method prevented mechanical destruction of the anion exchange resin. After leaching was completed, the resin was separated from the pulp on a polypropylene sieve with a mesh size of 0.3 mm. The resin was washed with 100 ml of water. Wash water was combined with pulp. Next, the pulp was subjected to filtration. The precipitate was washed with water until the pH of the filtrate was neutral. Wash water was combined with the mother liquor. The precipitate was dried. The filtrate was evaporated to the initial volume of the solution. After that, a resin sample was taken for analysis on palladium. Dried sludge and filtrate were analyzed for palladium content. In addition, to verify the results, palladium from anion exchange resin was desorbed with a 25% solution of ammonia, diluted 2 times with distilled water. Eluates were also analyzed for palladium content. The results obtained as a result of the experiments are presented in table 1.

As follows from the data presented in Table 1, the degree of leaching of palladium without anion exchange resin is much lower than without adding it to pulps. Moreover, palladium was poorly leached with concentrated nitric acid and a mixture of hydrochloric and nitric acids ("aqua regia"). However, not all solutions undergo complete sorption leaching. At a concentration of nitric acid above 3 M, partial destruction of the anion exchange resin is observed, which was observed by a decrease in the resin mass. The loss of mass of anion exchange resin after 24 hours of contact with a 4 M solution of HNO ₃ +3 M NH ₄ NO ₃ amounted to 0.95 g (in terms of the weight of dry anion exchange resin in the NO ₃ form), which amounted to about 10% of the initial sample. In aqua regia, anion exchange resin has almost completely decomposed.

On the other hand, in the range of reagent concentrations of 2–3 M for HNO ₃ and 2–3 M for NH ₄ NO ₃ with the addition of anionite AN-31 to the pulp, almost complete leaching of palladium is achieved, while without anionite, the degree of leaching of palladium is only 65-70%.

Table 1 The results on the leaching of palladium from sludge from isotope production by various solutions in the presence of AN-31 anion exchange resin, in comparison with leaching without anion exchange resin The composition of the solution for leaching palladium Leaching of palladium from sludge with the addition of 10 g of anion exchange resin Anion-free leaching The content of Pd in the sludge, mg The content of Pd in solution, mg The content of Pd in the ion exchanger, mg The degree of sorption leaching Pd,% (% conversion of Pd to ion exchanger / total degree of leaching) The content of Pd in the sludge, mg The content of Pd in solution, mg The degree of leaching Pd,% 0.5 M HNO ₃ 56 0,0 44.0 44.0 87.7 22.3 22.3 1 M HNO ₃ 0,0 49.4 49.4 50.6 65.7 34.3 34.3 3 M HNO ₃ 42,2 0.1 57.7 57.8 53.6 47.4 47.4 * 4 M HNO ₃ 31.7 0.5 65.3 65.8 46.1 53.0 53.0 1 M HNO ₃ +1 M NH ₄ NO ₃ 46.0 0,0 53.6 53.6 69.9 30.1 30.1 2 M HNO ₃ +1 M NH ₄ NO ₃ 16.8 0,0 83.9 83.9 51.7 48.6 48.6 1 M HNO ₃ + 2M NH ₄ NO ₃ 17.1 0,0 82.6 82.6 50.9 48.9 48.9 2 M HNO ₃ + 2M NH ₄ NO ₃ but 0.2 99.7 99.9 35,2 64.7 64.7

The composition of the solution for leaching palladium Leaching of palladium from sludge with the addition of 10 g of anion exchange resin Anion-free leaching The content of Pd in the sludge, mg The content of Pd in solution, mg The content of Pd in the ion exchanger, mg The degree of sorption leaching Pd,% (% conversion of Pd to ion exchanger / total degree of leaching) The content of Pd in the sludge, mg The content of Pd in solution, mg The degree of leaching Pd,% 3 M HNO ₃ + 2 M NH ₄ NO ₃ but 0.6 99.3 99.9 32,0 67.8 67.8 2 M HNO ₃ +3 M NH ₄ NO ₃ but 0.7 99.3 one hundred 31.5 68.5 68.5 3 M HNO ₃ +3 M NH ₄ NO ₃ but 2,3 97.6 99.9 27.0 72.5 72.5 * 4 M HNO ₃ +3 M NH ₄ NO ₃ but 3.6 96.3 99.8 72.8 72.8 15.7 M HNO ₃ at a temperature of 120 ° C 36,4 63.6 63.5 15.7 M HNO ₃ at a temperature of 95 ° C 28,2 72.0 72 ^** HCl _conc + HNO _conc in a ratio of 3: 1 (known vodka) 24.5 75.5 the resin dissolved 75.5 25.7 74,2 74,2 ^* partial dissolution of anion exchange resin; ^** complete dissolution of anion exchange resin

Thus, a decrease in the concentration of nitric acid in leaching solutions below 2 M leads to a decrease in the degree of sorption leaching, and an increase in its content above 3 M contributes to the intense destruction of anion exchange resin.

Example 2. 5 g of crushed palladium-containing sludge was poured into 100 ml of a solution containing 130 g / l of nitric acid and 150 g / l of ammonium nitrate. 15 ml of AN-31 resin was injected into the pulp. The amount of palladium in the sludge was 0.168 g. After leaching for 24 hours, the resin was separated from the pulp and washed with water. Next, palladium from the resin was desorbed with a 12% ammonia solution. The volume of the obtained eluate was 200 ml. The eluate was analyzed for impurities. The data obtained are presented in table.2. At the same time, palladium was leached with a solution of 2 M HNO ₃ containing 2 M NH ₄ NO ₃ . After leaching, the precipitate was separated from the solution by filtration and also analyzed for impurities (table 2).

Table 2 The content of palladium and impurities in solutions obtained after leaching of palladium by a known method and in eluates after sorption leaching of sludge

The content of the main components in the initial sludge,%: Pd - 3.36; Cu - 34; Fe - 23.1; Cr 4.9; Ti - 0.1; Zn - 1.9; Cd 0.1; Al - 8.7

Solutions The content of palladium and impurities, g / l Pd Cu Fe Cr Ti Zn Cd Al A solution of concentrated nitric acid (prototype) 0.48 22.36 1.31 1.20 0.09 2.91 0.34 0.38 Eluates after desorption of palladium from anion exchange resin AN-31 0.835 0.003 0.002 0.003 not found. not found. not found. not found.

The data obtained showed that with a high degree of leaching of palladium from sludge 99.4% (prototype 57%), the eluates obtained after desorption of palladium from anion exchange resin contain a small amount of impurities. The metal, which was obtained from solutions by reduction with hydrazine, contained less than 0.1% impurities.

Example 3. To determine the required amount of resin sorption leaching of palladium in the pulps were introduced various weights of anion exchange resin AN-31. The initial pulp was prepared as in the previous example. A sample of sludge in an amount of 5 g was poured into 100 ml of a solution with a concentration of nitric acid and ammonium nitrate, 2 M each reagent. Then AN-31 anion exchange resin was added to the pulps in the amount of 1, 3, 5, 8, 10 g. After leaching, the resin was separated from the pulp, and the palladium content was determined in it. As described in Example 1, solutions and sludge were analyzed. According to the results obtained, the degree of leaching of palladium was determined (Table 3). From the data given in Table 3, it follows that with the introduction of 1 g of anion exchange resin per 30 mg of palladium, the degree of leaching of palladium reaches more than 98%.

Table 3 The degree of leaching of palladium from the sludge, depending on the amount of AN-31 introduced into the pulp The amount of anion exchanger AN-31 in the pulp, g The content of Pd in the sludge, mg The content of Pd in solution, mg The content of Pd in anion exchange resin, mg The degree of transition of palladium to anion exchange resin,% The total degree of leaching of palladium,% one 60,2 44.1 63.3 37.7 63.9 3 11.2 4.9 152.0 90.5 93,4 5 1,5 1,1 165.5 98.5 99,2 8 0.8 Not an update 167 99,4 99,4 10 not upd. Not an update 167 99,4 99,4

Example 4. To establish the optimal ratio of W: T in the pulps, a series of experiments was carried out in which different volumes of leachable solution (25 ml, 50 ml, 75 ml, 100 ml) with a concentration of reagents were taken for 5 g of sludge and 5 g of ion exchanger. specified in example 3. The results of the experiments are summarized in table 4.

Table 4 The degree of leaching of palladium, depending on the ratio of W: T The volume of solution for leaching, ml The content of Pd in the sludge, mg The content of Pd in solution, mg The content of Pd in anion exchange resin, mg The degree of transition of palladium to anion exchange resin,% The total degree of leaching of palladium,% 25 12.3 not upd. 155.9 92.8 92.8 fifty 2.1 not upd. 165.7 98.6 98.6 75 1.3 1,1 165.5 98.5 99,2 one hundred 0.9 1,1 166.3 99 99.6 150 0.8 1,1 166.3 99 99.7

From this example it follows that the minimum ratio W: T should be 5: 1. A further decrease in the ratio of liquid to solid phase leads to a decrease in the degree of leaching of palladium. In addition, at low values of the ratio W: T, the process of separating the resin from the pulp is complicated.

The increase in the ratio W: T over 20 is impractical, as it leads to an additional consumption of reagents. It follows that the optimal ratio of W: T during leaching, which provides a high degree of extraction of palladium from sludge and does not lead to excessive consumption of reagents, lies in the range 1: 10 ÷ 1: 20.

Thus, the use of the proposed method allows you to:

a) significantly increase the degree of leaching of palladium from sludge in one stage;

b) to obtain pure solutions of palladium upon its desorption from anion exchange resin;

c) reduce the number of operations of the subsequent technology for processing solutions with the aim of obtaining palladium or its compounds, which in turn leads to a reduction in the consumption of reagents, the number of pieces of equipment and a reduction in working hours for servicing the redistribution of palladium.

Claims (4)

1. The method of leaching palladium from sludges containing palladium in the form of metal, oxide and metal oxide forms using a solution of nitric acid, characterized in that the leaching of palladium is carried out with solutions of nitric acid with the addition of ammonium nitrate and weakly basic epoxy polyamine type anion exchange resin AN-31, followed by separation of the anion exchange resin from the pulp, washing it with water and desorption of palladium from the anion exchange resin with an ammonia solution. 2. The method according to claim 1, characterized in that the concentration of nitric acid in the leach solution is maintained within 120-190 g / l, and ammonium nitrate 160-240 g / l. 3. The method according to claim 1, characterized in that the ratio of sludge: solution during leaching is maintained within the range of 1: 10-1: 20. 4. The method according to claim 1, characterized in that the anion exchange resin is introduced into the leaching pulp of palladium in an amount of at least 1 g per 30 mg of palladium contained in the sludge.