The method of separation of platinum and rhodium in hydrochloric acid solutions

 

(57) Abstract:

The invention relates to hydrometallurgy of precious metals and can be used for the separation of platinum group metals (PGM), in particular platinum and rhodium, in hydrochloric acid solutions by means of sorption using strong-base anion exchange resin. The invention allows for the possibility of obtaining in the process of separation of high-purity compounds of rhodium and platinum metal, reducing the loss of platinum, the reduced sorbent, reducing the complexity of the method and its simplification. To do this, before adsorption of hydrochloric acid solution partially precipitated platinum compounds with ammonium chloride solution, the sorption of lead by filtering through a bed of sorbent to saturation of the anion ions of platinum. For washing of the sorbent using 5 - 7 M solution of hydrochloric acid. Washed three times ionized platinum sorbent is exposed to the reducing agent solution of hydrazine-hydrate, after which the sorbent is maintained at 350 - 400C for 2 - 2.5 hours in a reducing environment, and then fired at 950 - 1000C. the ammonium chloride is used in a quantity sufficient to maintain the ratio of platinum : rhodium in solution 1: is used for the separation of platinum group metals (PGM), in particular platinum and rhodium, in hydrochloric acid solutions by means of sorption with obtaining metal platinum and pure compounds of rhodium.

The known method of sorption separation of precious metals (The separation of noble metals by ion changers containing S-honded dithizone and dehydrodithizone as functional groups. Grote M., Kettrup A. "Ion Exch. Technol. " Chichester, 1984, 618-625). As sorbent with anion exchange properties used specially synthesized resin P-TD, containing 1.1 mol tetryzoline groups in 1 g of dry resin.

The known method is based on the use of specially synthesized sorbent, which significantly increases the cost of implementation of the method.

A common feature of known and claimed methods of separation of PGM is sorption on the sorbent with anion exchange properties.

Known hydrometallurgical processes for the separation of platinum group metals in chloride environment (Hydrometallurgical processes for the separation of platinum group metals (PGM) in chloride media. Warshawsky, A., "Ion Exch. Technol". Chichester, 1984, 604-610).

For the separation of PGMs from other metals using sorption on the weakly basic anion exchange resin in acidic medium by ion-exchange mechanism with subsequent desorption. For the subsequent separation of PGM in the process of solvent extraction is conducted rapid GE cationic or neutral complexes. As extractant used tertiary amines. Pt and Pd are transferred to the organic phase, and Rh and Ir remain in the aqueous phase, and Pt and Pd share on stage Stripping using NH2-CS-NH2and SCN-ion.

The known method is distinguished by the small size of the weakly basic anion exchange resin for ion PGM, lack of selectivity, the use of expensive reagents for desorption, and the complexity and complexity in its implementation.

Common to the known and declared methods is the implementation of sorption separation on anion exchange resin and the concentration of rhodium in the aqueous phase.

The closest, the technical nature of the claimed is a method of separation of rhodium and platinum in hydrochloric acid solutions on strong-base anion exchange Separation of Rhodium (III) - Platinum (IV) and Iridium (III) Platinum (IV) on VARION AT 400 and VARION AT 660 changers. K. Brajter, K. Stonawska, Z. Vorbrodt. "Chemia Analityczna", 24, 1979, 766-768).

According to a known method the separation of platinum and rhodium was carried out in 3-molar (3 M) hydrochloric acid solution. A solution containing platinum and rhodium, were made in several stages with the Royal vodka for oxidation of platinum to platinum (IV), after which the solution was cooled and passed through a column containing celineonline the deposits of rhodium was washed out of phase sorbent 3 M solution of hydrochloric acid. This wash solution was contaminated with ions of platinum due to joint washout of the initial solution and desorption of rhodium. The sorbent containing platinum were removed from the column, dried and burned at a temperature of 700oC with obtaining metal platinum.

The known method does not allow to obtain high-purity compounds of rhodium, to avoid possible significant losses of platinum combustion sorbent and reduce the concentration of rhodium in the eluate due to dilution proryvnym solution. In addition, the known method is distinguished by high consumption used in the process of sorbent at high concentrations of platinum in the solution, the difficulty and complexity of the preparation of the solution supplied to the sorption column.

To the General characteristics of the known and the claimed method include sorption on strong-base anion exchanger with obtaining hydrochloric acid rhodium solution, washing the sorbent with hydrochloric acid and the burning of the sorbent with obtaining metal platinum.

The invention is aimed at providing opportunities during the separation of high-purity compounds of rhodium and platinum metal, reducing the loss of platinum, reducing the complexity of the method and its UPA and rhodium in hydrochloric acid solutions, including sorption on strong-base anion exchanger with obtaining hydrochloric acid rhodium solution, the washing of the sorbent and its subsequent combustion of obtaining metallic platinum, before sorption of hydrochloric acid solution partially precipitated platinum compounds with a solution of ammonium chloride. The sorption of lead by filtering through a bed of sorbent to the saturation of the last platinum ions. Rich platinum sorbent after washing 5-7 M solution of hydrochloric acid is treated with hydrazine hydrate. Before combustion sorbent at a temperature of 950-1000oC it is subjected to thermal decomposition at a temperature of 350-400oC for 2-2,5 hours in a reducing environment. The ammonium chloride is used in an amount necessary to maintain the ratio of platinum:rhodium in the solution is 1:2.

The method of separation of platinum and rhodium is carried out as follows.

Source hydrochloric acid solution obtained after electrochemical dissolution of an alloy of platinum with rhodium, is the concentration of the hydrochloric acid equal to about 5.5 to 6.5 mol/DM3the concentration of platinum and rhodium respectively 120 g/DM3and 48 g/DM3. The solution was diluted with demineralized water to a concentration of 2.5 mol/DM3

After removal by filtration of the resulting precipitate - hexachloroplatinate ammonium - mother solution with the content of platinum in the amount of 9.2 g/DM3and rhodium 18,5 g/DM3sent on sorption separation, using as a sorbent strong basic anion exchange resin of one of the grades (see table).

As can be seen from the table, capacitance (CE) highly basic anion exchange resin for ion platinum is significantly higher than the corresponding values for the rhodium ions, so in the process of adsorption in dynamic conditions is achieved quantitative separation of these metals.

Separation of platinum and rhodium was carried out on the cascade of four columns to the saturation of the first column of the cascade platinum ions, after which the column out of the process at the stage of leaching; the second column was the first and so on

The content of the basic substance - rhodium - Sol is Oh 18 g/DM3.

Ionized platinum sorbent was subjected to three washing of 6 M hydrochloric acid, then with demineralized water until pH 4-5 to remove the mother liquor from the adsorbent and desorption partially sorbed ions rhodium.

Washing solutions containing platinum and rhodium, were combined with the mother liquor.

The washed sorbent is saturated with ions of platinum and containing rhodium ions were subjected to impact of a 20% aqueous solution of hydrazine hydrate, which was restored platinum granules of the anion to the metal, making it possible to significantly reduce the loss of platinum in the subsequent burning of the sorbent. Before burning the resulting sorbent was subjected to thermal decomposition at a temperature of 400oC for two hours without access of air, which provides dopostavleno remaining in the resin of platinum compounds. Then burned the sorbent in an atmosphere of air at a temperature of 950oC with getting spongy platinum purity not less than 99,93%. When this capacity is involved in the process of absolutely dry sorbent brand AV-17-10P on platinum was 650 mg/g, much higher than the capacitive characteristics of other processes.

Thus, the set s, the possibility of obtaining the separation of high-purity compounds of rhodium and platinum metal, reducing the loss of platinum. The proposed method is simple, not time consuming and reduces the flow rate of the sorbent.

1. The method of separation of platinum and rhodium in hydrochloric acid solutions, including sorption on strong-base anion exchanger with obtaining hydrochloric acid rhodium solution, the washing of the sorbent and its burned to produce metallic platinum, characterized in that before the sorption of hydrochloric acid solution partially precipitated platinum compounds with ammonium chloride solution, the sorption of lead by filtering through a bed of sorbent to its saturation platinum ions, washing the sorbent using 5 - 7 M solution of hydrochloric acid affect the sorbent solution of hydrazine hydrate, and before combustion sorbent at 950 - 1000oC it is subjected to thermal decomposition at 350 - 400oC for 2 - 2.5 hours in a reducing environment.

2. The method according to p. 1, characterized in that the ammonium chloride solution taken in the quantity necessary to maintain the ratio of platinum:rhodium in the solution is 1:2.

 

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FIELD: noble metal hydrometallurgy.

SUBSTANCE: invention relates to method for acid leaching of platinum method from secondary raw materials, in particular from ceramic support coated with platinum metal film. Target metals are leached with mixture of hydrochloric acid and alkali hypochlorite at mass ratio of OCl-/HCL = 0.22-0.25 and redox potential of 1350-1420 mV.

EFFECT: decreased leaching temperature, reduced cost, improved platinum metal yield.

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