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INVENTION
Russian Federation Patent RU2171855
METHOD OF EXTRACTION OF PLATINUM METALS FROM SLUDGE
Name of the inventor: Timofeev NI .; Bogdanov VI .; Ermakov AV .; Sivkov MN .; Gorbatova LD .; Korepanov SS .; Lavrov AA
The name of the patentee: OJSC "Ekaterinburg plant for processing non-ferrous metals"
Address for correspondence:. 620014, Ekaterinburg, Lenina, 8, of "EZ OCM", Deputy Director V.I.Bogdanovu
Starting date of the patent: 2000.01.05
The invention relates to a hydrometallurgical precious metals and can be used for extracting platinum group metals from the sludge produced in the production of nitric acid. The method includes leaching a slurry, which is carried out in two steps with separation of the solution and washing the cake after each step, the first leaching step is carried out in hydrochloric acid, and the second - in a mixture of concentrated hydrochloric acid and nitric acid, and the filter cake after the initial leaching step is calcined at a temperature of 800 -900 ° C for 1 hour, and then passed to a second leaching step. Solutions and washings are combined both leaching stages, corrected for the content of platinum metal to 5-50 g / l and the resulting solution of platinum metals are removed by precipitation to obtain a precipitate which is calcined and melted on the ingot. Leaching is carried out at a temperature of 80-95 ° C. Precipitation from a solution of platinum group metals is carried out depending on the content in the platinum group in the following ways: hydrazine at pH 2-4 and a temperature of 70-80 ° C to obtain a bulk concentrate of platinum metals; ammonium chloride, at pH less than 2 and a temperature of 40 ° C to yield the ammonium chloroplatinate; precipitation using electrolysis. The method allows to increase the degree of extraction of platinum metals and sludge due to the optimal sequence and combination of technological methods, providing almost complete translation of platinum group metals in the leaching solution.
DESCRIPTION OF THE INVENTION
The invention relates to a hydrometallurgical precious metals and can be used for extracting platinum group metals from the sludge produced in the production of nitric acid.
Sludges resulting from the production of nitric acid are fine particulate material complex chemical, phase composition of the material and in which the total content of platinum group metals (platinum, palladium and rhodium) is in the range 0.5 - 80%. In this regard, the sludges are an additional source of platinum metals. But at the same time the sludge recycling is extremely challenging, since these are present in the platinum group metals and other related chemicals are in the form of compounds differing in chemical properties (acid interaction).
The method for extracting platinum group metals from the containing material (Patent RF N 2120485, C 22 B 11/00, appl. 07/03/97 was, publ. 20.10.98, at b. "Inventions", N 29, p. 363 ). The method comprises melting a feedstock handling ingot aqua regia solution and precipitation of metals from the platinum tsarskovodochnogo solution to prepare a slurry containing gold, silver chloride, and hlorpalladat chloroplatinate.
The disadvantage of this method is multistage and significant deadweight losses PGE on pyrometallurgical operations, which reduces the degree of extraction of precious metals. A known method can be effectively applied for the treatment of a material containing platinum group along with gold and silver.
There is a method of extraction of platinum together with rhodium from waste generated in the nitrogen industry (Poland Patent 139 177 N, C 22 B 7/00, appl. 06/03/83, at publ. 31.07.87g., AJ "Metallurgy", 88 g , 3G265P, p. 28). The method comprises alloying slurry with alkali (NaOH or KOH) at the temperature of 450 - 650 o C. The melt is leached with water, the precipitate was repeatedly treated with hydrochloric acid oxidant additives. From the resulting solution of platinum and palladium is reduced with aluminum or zinc. The whole cycle is repeated many times.
However, a disadvantage of this method is the low degree of extraction of platinum metals as aluminum used as a reducing agent or zinc underperforms for complete extraction of metals from the platinum-containing solution thereof.
Further, recontamination occurs platinoidosoderzhaschego solution of ferrous metals, and the use of fusion at 2.5 parts to 1 part of alkali slurry process complicates the subsequent filtering and processing solution.
According to the technical nature of the closest object to the proposed invention is a method of extracting platinum slimes - nitric acid production waste (copyright certificate N 45936 Bulgaria, C 22 B 11/04, appl 31.05.88, published 09.15.89, the "Inventions.. countries of the world, "vol. 48, N 2, 92, p. 1-2).
The method comprises processing the slurry containing platinum and related elements in the form of various chemical compounds with a mixture of concentrated hydrochloric and nitric acids in a single batch or slurry introduction. Dissolution is carried out at a temperature of 333-385K, pressure of 0 - 6 atm. for 8 - 12 hours, and isolation of the platinum solution is carried out by extraction with an organic reagent.
The disadvantage of this method is the low degree of extraction of platinum metals, since the method does not provide a sufficient opening of PGE compounds and the use of expensive and scarce reagents.
Furthermore, known technology involves the necessity of disposal of organic reagents used in the extraction process because they contaminate solutions.
The technical result of the invention is to increase the degree of extraction of platinum metals in the processing of sludge generated in the production of nitric acid.
Technical result is achieved by a method for extracting platinum group metals from the sludge produced in nitric acid comprising the acid leaching batch introducing sludge and subsequent recovery of platinum group metals from a solution according to the invention the leaching is carried out in two steps with separation of the solution and washing the cake after each stages, a first stage leaching is carried out in hydrochloric acid, the second - in a mixture of concentrated hydrochloric acid and nitric acid, and the filter cake after the first stage leaching is calcined at a temperature of 800 - 900 o C for 1 hour, and then passed to a second stage leach solution and after both washings leaching stages combined, corrected for the content of platinum metal and platinum metal is precipitated, the resulting precipitate was calcined and melted at the ingot.
The leaching process slurry is carried out at a temperature of 80 - 95 o C, the combined solution after leaching and leaching cake corrected content therein amounts of platinum group metals to 5 - 50 g / l, and the precipitation scheduled metals from the resultant solution is carried out in dependence on its content of PGE : or hydrazine at pH 2-4 and a temperature of 70 - 80 o C to obtain a bulk concentrate of platinum metals, or ammonium chloride at a pH less than 2 and a temperature of 40 o C to yield the ammonium chloroplatinate and / or by electrolysis.
Essence of the method is as follows
In the claimed method, the leaching process is carried out in two stages. The first leaching step, conducted at a temperature of 80 - 90 o C in hydrochloric acid, is preparatory and provides a translation into the main part of the base metal solution (mainly iron and its compounds). This avoids the subsequent sintering sludge firing operation. Simultaneously at this stage it moves to a solution of 15% platinum and 20% rhodium and palladium from the original amount.
The operation burning sludge to the second leaching stage provides translation sparingly soluble compounds of platinum group metals in the acid form and their almost complete transition to the solution in a subsequent second stage leach. As shown by differential thermal analysis (DTA) conducted on Kekaha, this effect is due to take place during the firing process of destruction insoluble in hydrochloric acid and aqua regia PGE compounds that were previously in the form of oxides and complex salts.
Selecting the firing temperature in the range of 800-900 o C is due to the fact that phase transitions occur at these temperatures and platinum metals are moving in the acid form, and the loss of platinum group metals are minimal. At temperatures below 800 o C reaction destruction PGE compounds and their transition to a soluble form requires a long exposure, and at temperatures above 900 o C may melt cinder that will reduce the platinum group metals in the extract solution.
It was established experimentally that the firing duration 1 Hour is optimal - following the firing of the acid leach was the same regardless of the increase in duration of 1.5, 2 and 3 hours.
The duration of firing at least 1 hour the claimed temperature range reduces recoveries of platinum group metals in solution.
After firing, the slurry is directed to the second leaching step which is carried out at a temperature of 80 - 95 o C in a mixture of concentrated hydrochloric and nitric acids. At this stage is reached the maximum possible recovery of the platinum metals into solution.
The process is most intensively proceeds at the same temperature, but not higher than 95 o C, since further increase in temperature leads to a considerable evaporation of the leach solution.
Stated temperature range is sufficient for the experimentally determined the duration of leaching, which is no more than 1 hour.
Solutions after filtration and washing were combined and adjusted to a volume corresponding to the PGM content of 5-50 g / l, and recovered from the resulting solution by precipitation of the platinum metals under conditions determined by their content in the solution, which in turn depends on the composition of the starting sludge.
When extracting platinum group metals from a solution containing platinum, palladium and rhodium in significant quantities (up to 50 g / l), the deposition is conducted with hydrazine to obtain a bulk concentrate platinum group metals.
In order to achieve the fullness of their deposition the best option is the implementation process at pH 2-4 and a temperature of 70 - 80 o C, while non-ferrous metals and chlorides of iron present in the solution are not hydrolyzed to precipitate.
The limits of pH values due to the fact that the pH value falls below 2 extracting platinum group metals from a solution, while increasing over 4 - sludge filterability deteriorates due to the formation of iron hydroxide (III).
The temperature range is set experimentally and given the acidity of the solution ensures the lowest consumption of the reducing reagent.
Advantageous at high platinum content in its solution previously removed from the solution by precipitation with ammonium chloride at pH less than 2 and a temperature of 40 o C to yield the ammonium chloroplatinate, wherein palladium and rhodium are in solution, which is then removed by known methods.
Electrochemical deposition method using electrolysis is effective for dilute solutions in which the total content of platinum group does not exceed 5 g / l. To remove PGE from such solutions using volume-porous electrodes, used electrolysis solutions contain unrecoverable amounts of platinum metals, so you only need to carry out their neutralization and disposal.
Obtained after deposition of each particular method of powder was filtered, washed, dried at a temperature of 150 o C, and then melted to produce a high-grade ingot.
DETAILED DESCRIPTION OF THE INVENTION (examples).
example 1
Initial sludge, containing platinum, palladium and rhodium charged portions heated to 40 o C and strong hydrochloric acid with constant stirring of the pulp was adjusted to a temperature of 90 o C, at which the leaching process was carried out. The pulp is then cooled to a temperature of about 40 o C, filtered, the solid (cake) on a filter, washed with water and transferred to firing.
The cake was charged to a muffle furnace material is warmed for 1.5 - 3 hours to a temperature of 850 o C, and calcined at this temperature for 1 hour.
The calcined material (calcine) was re-leached in a mixture of concentrated hydrochloric and nitric acids (tsarskovodochnoe leaching) under the same conditions as in the first leaching stage.
After the leaching, the pulp was filtered, the cake washed with water.
The resulting solutions and washings were combined and evaporated to a volume corresponding to the sum of the content of platinum metal in which processing solution may be carried out.
Extraction was carried out by platinum metal deposition is performed as follows.
Solution previously neutralized to pH 2 by addition of sodium hydroxide solution. At a temperature of 70 - 80 o C and gradually added with continuous stirring hydrazine solution. The precipitated powder platinum metals were filtered, washed and dried at 150 o C, then melted into an ingot.
example 2
Roasting and leaching of the starting slurry was performed under the same conditions as in Example 1.
The resulting solution containing the predominant amount of platinum, treated in order to isolate the platinum as ammonium chloroplatinate (CPA) as follows.
With constant stirring, was added portionwise ammonium chloride solution. The process of deposition was carried out at ~ 40 o C at pH = 2. The precipitate was filtered and washed with CPA acidified with 5% aqueous ammonium chloride until colorless washing water.
From the washed CPA received platinum in metallic form by known methods and then melted.
The mother liquor containing palladium and rhodium, processed by known deposition techniques.
example 3
Is tested sludge with a low content of platinum metals.
Roasting and leaching was conducted under the same conditions as in Example 1.
Obtained in leaching solutions had a total content of PGE 5.9 g / l.
To extract from such PGM solution using an electrochemical deposition method using the cell of flowing volume-porous electrodes.
example 4
For comparative data recoveries of platinum group metals from slimes tests were carried out under conditions known method, in the absence of sludge firing operation.
Experience included leaching of the original sludge at a temperature of 80 o C with a mixture of concentrated hydrochloric acid and nitric acid, separating and washing the precipitate and deposition of platinum group metals from the resulting solution.
Results obtained from testing of various sludge samples, their initial composition, the composition of the intermediate and final products are presented in the table.
Thus, the proposed method can significantly improve the recovery of platinum group metals from the sludge by the optimal sequence and combination of technological methods, providing almost complete translation of platinum group metals in the leaching solution and obtain an ingot with a high content of precious metals
CLAIM
1. A process for extracting platinum group metals from the sludge produced in the production of nitric acid, comprising an acid leach slurry batch introduction and subsequent extraction of platinum metals from solution, characterized in that the leaching is carried out in two steps with separation of the solution and washing the cake after each stage, the first leach step is carried out in hydrochloric acid, the second - in a mixture of concentrated hydrochloric acid and nitric acid, and the filter cake after the first stage leaching is calcined at a temperature of 800-900 o C for 1 hour and then fed to the second leaching step, solutions and after washings both leaching stages combined, corrected for the content of platinum metal and platinum metal is precipitated, the resulting precipitate was calcined and melted at the ingot.
2. A method according to claim 1, characterized in that the leaching is carried out at a temperature of 80-95 o C.
3. The method of claim 1, wherein the deposition of platinum metal from the solution is carried out with hydrazine at pH 4.2 and a temperature of 70-80 o C to give bulk concentrate platinum group metals.
4. The method of claim 1, wherein the deposition of platinum with ammonium chloride solution is carried out at a pH less than 2 and a temperature of 40 o C to yield the ammonium chloroplatinate.
5. The method of claim 1, wherein the deposition of platinum metal from the solution is carried out by electrolysis.
6. A method according to claim 1, characterized in that the deposition of lead solution containing amounts of platinum metal 5-50 g / L.
print version
Publication date 14.03.2007gg
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