RU2223918C1 - Ruthenium concentration method - Google Patents

Abstract

FIELD: inorganic compounds technology. SUBSTANCE: invention relates to liquid extraction-mediated isolation of ruthenium from solution and, more particularly, consists in that ruthenium is extracted from nitrite anion-containing solution with phosphoric acid tributyl ester. After extraction, organic phase is washed with sodium nitrite solution having 250 g/l salt content and reextracted with sodium hydroxide solution having 10-100 g/l alkali content. As nitrite anion-containing solution, mother liquor remaining after precipitation rhodiumand/or iridium-ammonium hexanitrite. Purity of ruthenium product is at least 95%, 99% of which is recovered being concentrated by a factor of 18-20. EFFECT: increased purity and degree of recovery of desired product. 2 cl, 2 tbl

Description

 The invention relates to the separation of ruthenium from solutions by liquid extraction.

 In many cases, when processing ores, waste, intermediates, etc. containing platinum group metals (PGM), ruthenium is in solution.

 Various methods exist for extracting ruthenium from these solutions.

 One of them is liquid extraction. It allows, firstly, to concentrate ruthenium, and secondly, to clear it of the accompanying impurities of both PGM and base metals.

 A variety of extractants have been proposed for the extraction of ruthenium from solutions.

 Numerous studies have shown that the extraction of ruthenium during extraction with various classes of extractants varies depending on the chemical state of ruthenium in the aqueous phase and the nature of the organic phase.

 It is known that in nitric acid solutions ruthenium forms easily hydrolyzed nitrosonitrate complexes and more stable nitrosonitro complexes.

For example, a method is known for extracting ruthenium from aqueous nitric acid media using dialkyldithiophosphoric acid in the presence of a compound capable of replacing the nitroso group of NO ⁺ in the ruthenium complex. These compounds are sulfamic acid or hydrazine (US 4282112, C 01 G 55/00, 08/04/1981).

 The disadvantage of this method is the need for introducing additional reagents into the solution and the use of expensive extractants.

 In addition, the method is not intended to extract ruthenium from solutions containing other PGMs.

 The known process of concentrating ruthenium from nitric acid media using more accessible extractants, such as tributyl ether phosphoric acid (TBP), trioctylamine (TOA), trioctylphosphine oxide (TOPO).

 The process of re-extraction of ruthenium from TBP was carried out with alkali (1 M NaOH solution) (Sinitsin N.M., Pichkov V.N. "On the re-extraction of nitroso complexes of ruthenium", Radiochemistry, Leningrad, Nauka, 1968, v. X, v.6, p. 715-716).

 However, it is known that during TBP extraction all PGMs go into the organic phase (M. Meretukov, Liquid extraction processes in non-ferrous metallurgy, Moscow, Metallurgy, 1985, p. 185).

 Closest to the proposed is a method of concentrating ruthenium from a solution, including extraction with phosphoric acid tributyl ether from a solution containing nitrite anions.

 It was found that in the presence of nitrite anions, the distribution coefficient of ruthenium increases significantly. The molar ratio of nitrite anion to ruthenium should be greater than 1, mainly at least 10: 1 (US 2894816, C 01 G 55/00, 07/14/1959).

 The disadvantage of this method is that when concentrating ruthenium from solutions containing other PGM or base metals, the solution is not sufficiently pure.

 The objective of the invention is to provide such a method for concentrating ruthenium, the result of which would be to obtain a solution of ruthenium of high purity with high extraction of ruthenium.

 For this, in the method of concentrating ruthenium from a solution, including extraction of phosphoric acid with tributyl ether from a solution containing nitrite anions, after extraction, the organic phase is washed with a solution of sodium nitrite with a concentration of at least 250 g / l and reextraction with a solution containing sodium hydroxide concentration of 10- 100 g / l

 As a solution containing nitrite anions, you can use the mother liquor after precipitation of ammonium hexanitrite rhodium and / or iridium.

 The method is as follows.

The initial solution contains Hcl 10-15 g / l, NO ₂ ^- 100-170 g / l, Ru 0.5-5 g / l, Rh up to 30 g / l, Ir up to 30 g / l, Pt 1.5- 15 g / l, Pd 1.5-15 g / l, Cu less than 2 g / l, Ni less than 2 g / l. This solution is contacted with an undiluted TBP solution, extracting ruthenium. Ruthenium is extracted into the organic phase in the form of nitrozonitro complexes.

 As initial solutions for extraction, a mother liquor can be used after precipitation of ammonium hexanitrite rhodium and / or iridium (ANG).

This solution has the composition NH ₄ Cl 100-200 g / l, NO ₂ ^- 100-170 g / l, Ru 0.5-5 g / l, Rh up to 2 g / l, Ir up to 2 g / l, Pt up 5 g / l, Pd up to 5 g / l, Cu less than 2 g / l, Ni less than 2 g / l.

 After extraction, the organic phase (extract) is washed with a solution of sodium nitrite with a concentration of at least 250 g / l.

 In this case, Ir, Rh, Pt, Pd, Cu, Ni are washed out in the washing solution.

 If you use a solution of sodium nitrite with a concentration below 250 g / l, then increases the extraction of ruthenium in the wash solution, i.e. provides its general extraction during the extraction process.

 The upper limit of the concentration of sodium nitrite is determined by its solubility.

 After washing, ruthenium is re-extracted with a solution containing sodium hydroxide concentration of 10-100 g / l.

 If the concentration of sodium hydroxide is below 10 g / l, then the created alkalinity of the medium is not enough to completely extract ruthenium.

 An increase in the concentration of sodium hydroxide above 100 g / l is impractical, because does not lead to an increase in the degree of re-extraction of ruthenium.

 The invention is illustrated by the following examples.

 Example 1

The initial solution contains Hcl 12 g / l, NO ₂ ^- 150 g / l, Ru 1.5 g / l, Rh 8 g / l, Ir 15 g / l, Pt 3 g / l, Pd 4.9 g / l , Cu 10 mg / L; Ni 150 mg / L.

This solution is contacted with TBP in an extraction cascade at a volume ratio of organic and aqueous phases of V _o : V _in = 1: 2.9. The number of extraction steps is 7.

At the next 5 steps of the cascade, the organic phase is washed with a solution containing 300 g / l sodium nitrite at a volume ratio of organic and aqueous phases of V _o : V _in = 1: 0.15.

Then, at 5 steps, reextraction is carried out with a solution containing sodium hydroxide concentration of 30 g / l with a volume ratio of organic and aqueous phases of V _o : V _in = 1: 0.15.

 Wash solution, raffinate (aqueous phase after extraction) and re-extract are analyzed for the content of ruthenium and other PGMs.

 The results are presented in table 1.

 The purity of ruthenium obtained by a known method is 70%.

 The purity of ruthenium obtained by the claimed method is at least 95%, while the extraction of ruthenium is more than 99%.

Example 2
The initial solution after deposition of ANG contains NH ₄ Cl of 150 g / l, NO ₂ ^- 150 g / l, Ru 1 g / l, Rh 0.3 g / l, Ir 0.5 g / l, Pt 2 g / l, Pd 1.5 g / l, Cu 500 mg / l, Ni 500 mg / l.

This solution is contacted with TBP in an extraction cascade at a volume ratio of organic and aqueous phases of V _o : V _in = 1: 2.9. The number of extraction steps is 7.

The following 5 stages cascade carried washing the organic phase with a solution containing 250 g / l of sodium nitrite in a volume ratio of organic and aqueous phases V _o: V _in = 1: 0.15.

Then carry out a back extraction with a solution containing sodium hydroxide concentration of 50 g / l with a volume ratio of organic and aqueous phases V _o : V _a = 1: 0.15.

 Wash solution, raffinate (aqueous phase after extraction) and re-extract are analyzed for the content of ruthenium and other PGMs.

 The results are presented in table 2.

 The purity of ruthenium obtained by the claimed method is at least 95%, while the extraction of ruthenium is more than 99%.

 The presented data show that the claimed method allows to extract ruthenium from solutions containing PGM and base metals, such as, for example, copper and nickel, with a high yield and high purity, while ruthenium is concentrated 18-20 times.

Claims (2)

1. A method of concentrating ruthenium from a solution, including extraction of phosphoric acid with tributyl ether from a solution containing nitrite anions, characterized in that after the extraction, the organic phase is washed with a solution of sodium nitrite with a concentration of at least 250 g / l and reextraction with a solution containing sodium hydroxide concentration of 10-100 g / l. 2. The method according to claim 1, characterized in that as a solution containing nitrite anions, a mother liquor is used after precipitation of ammonium hexanitrite rhodium and / or iridium.

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