RU2200132C1 - Method of recovering and separating platinum-group metals - Google Patents

Abstract

FIELD: precious metal technology. SUBSTANCE: method includes stripping of initial raw material by hydrochlorination, gold separation, extraction purification to remove nonprecious metal impurities, palladium extraction and platinum extraction, preparation of iridium and rhodium concentrate and their separation by extraction. Gold is separated by adjusting redox potential of solution to 500- 550 mV measured against normal hydrogen electrode. Platinum and/or palladium are recovered by simultaneous, but separate extraction from solution obtained after purification from non-precious metal impurities. Separate platinum and/or palladium extracts are therefore obtained. Platinum and/or palladium are then reextracted from these extract solutions. Raffinates obtained after extraction of platinum and palladium are combined and precipitate of platinum metals is formed by on-cathode electrolysis, after which cathodic precipitate is dissolved. Solution is further used for additional recovery of useful components. EFFECT: enabled integrated processing of various-type raw material, avoided formation of mother liquors, and increased degree of recovery and purity of products. 5 cl, 2 ex

Description

 The invention relates to the field of processing of raw materials containing platinum metals, and is intended for their extraction.

 Platinum metals are usually found in complex ores and concentrates, in anode sludge, in the form of a mixture of metals, oxides, sulfides and other compounds. These sources may also contain silver, gold, selenium, tellurium, as well as impurities of base metals: copper, nickel, iron, arsenic, antimony, tin, lead, bismuth, silicon, etc. Extraction of platinum metals (PGMs) from such raw materials and their separation is a difficult task.

 One of the methods for opening almost any type of raw material is hydrochlorination, i.e., dissolving the starting material in hydrochloric acid, through which chlorine gas is passed. Depending on the concentration of hydrochloric acid and the ratio of hydrogen chloride and chlorine, it is possible to autopsy both part of the compounds and all compounds contained in the starting material.

 No less difficult is the task of separating the platinum metals contained in the resulting solution. To solve it, extraction methods were developed.

 A known method of a three-stage processing of the feedstock with hydrochloric acid and chlorine gas. Separation and extraction of precious metals from aqueous chloride solutions is carried out by extraction.

 First, ruthenium and osmium are oxidized to tetroxides and removed from the solution. Gold, palladium and platinum are then extracted with dibutyl carbitol and are removed from the raffinate by extraction with alkyl sulfide and tributyl phosphate, respectively. Then, iridium, which was previously oxidized to the tetravalent state, is reduced and extracted with tributyl phosphate. Finally, rhodium is recovered (see US Pat. No. 4,390,366, C 01 G 7/00, 07/28/1983).

 The disadvantage of this method is the complex dissolution scheme of the feedstock, providing for the separate dissolution of platinum, palladium and ruthenium, rhodium, iridium and osmium with the intermediate fusion of insoluble residues and their re-dissolution. This leads to the appearance of a large number of solutions, the loss of valuable components.

 In addition, for any of the metals, it is provided for its isolation from the solution after extraction by chemical precipitation of the compound and then reduction to metal.

 This greatly complicates the process, leads to the formation of a large number of mother liquors that require further processing, because the content of platinum metals in them does not allow the discharge of these solutions. In addition, in the processes of extraction and stripping, it is necessary to carry out additional post-treatment of impurities that are extracted with noble metals.

 Another known method involves high-temperature gas phase chlorination to convert ruthenium, rhodium, osmium and iridium to a soluble state.

 The resulting cinder is subjected to dissolution by hydrochlorination in a chlorine-hydrochloric acid system.

 Extraction is used to separate platinum metals.

 First, gold is extracted into the organic phase with methyl isobutyl ketone and reduced from the organic phase to metal.

 Palladium is then recovered with a mixture of LIX64 and amine, osmium and ruthenium tetroxides are distilled off, and iridium is reduced.

 Then platinum is extracted with amberlite. Iridium is oxidized and recovered with an amine. Rhodium is isolated from the resulting solution by ion-exchange sorption (see US patent 3960549, C 22 D 11/04, 1976).

 The disadvantage of this method is the impossibility of obtaining pure products, because the impurities contained in the feedstock are separated only in the process of separation of platinum metals. Copper is removed by washing the organic phase in the palladium extraction step.

 Closest to the proposed method is the extraction and separation of platinum group metals, including opening the feedstock by hydrochlorination, gold separation, extraction purification from impurities of iron, tin and antimony, selective extraction of palladium to obtain a reextract containing palladium and raffinate containing the remaining PGMs, isolation palladium from the reextract and selective extraction of platinum from the raffinate to obtain a reextract containing platinum, and a solution of iridium and rhodium. From the reextract obtained after purification from impurities of iron, tin and antimony, PGM is electrochemically extracted, and the solutions obtained after extraction of palladium and platinum are purified from PGM by electrolysis (see patent RU 2161130, 27.12.2000).

 The objective of the invention is the creation of such a method that will allow for the integrated processing of raw materials of any kind, to eliminate the formation of mother liquors, to increase the extraction and purity of the resulting products.

 To solve this problem, in a method for the extraction and separation of platinum group metals, including opening the feedstock by hydrochlorination, gold separation, extraction purification from base metals, palladium extraction and platinum extraction, obtaining iridium and rhodium concentrate and their separation by extraction, gold separation is carried out by finishing redox potential of the solution up to 500-550 mV with respect to the normal hydrogen electrode, from the solution obtained after cleaning from impurities of metals, platinum and / or palladium are extracted by extraction in parallel, but separately, with the formation of separate extracts of platinum and / or palladium, then platinum and / or palladium are separately extracted from the extracts, the raffinates obtained by platinum extraction and / or palladium extraction are combined and precipitate from them a precipitate of platinum metals by electrolysis at the cathode, the cathode precipitate is dissolved, platinum and palladium are isolated from the solution to obtain a concentrate of iridium and rhodium.

 In addition, it is possible to carry out chlorination before hydrochlorination to produce sublimates of impurities, osmium and ruthenium, and cinder containing platinum group metals.

 In the event that oxide-sulfide concentrates of platinum metals are used as the feedstock, ammonium chloroplatinate is precipitated from the solution after separation of gold, it is dissolved and the resulting solution is sent for purification from base metal impurities.

 The method also provides that the insoluble hydrochlorination residue and / or cathodic precipitates obtained from solutions after extraction of the platinum group metals are chlorinated with chlorine in a molten chloride salt, the cinder is dissolved in hydrochloric acid, the resulting solution is purified from base metals by extraction, from the purified solution by extraction platinum is isolated, and then palladium, and iridium and rhodium are separated from the obtained raffinate by extraction.

 The iridium reextract obtained as a result of extraction separation of iridium and rhodium is subjected to electrochemical purification in the presence of organic substances: tributyl phosphate, and / or sulfoxides, and / or kerosene, and / or octanol.

 The claimed method is carried out in the following way.

 A platinum metal concentrate, for example KP-1, is purified from impurities of arsenic, selenium, tellurium, tin, antimony by low-temperature chlorination. At the same time, ruthenium and osmium are driven away. The resulting cinder is dissolved by hydrochlorination.

 In the case where raw materials use schlich platinum or secondary raw materials, the amount of impurities of arsenic, selenium, tellurium, tin, antimony in them is insignificant, and additional purification of impurities by chlorination is not required. These types of raw materials are immediately sent to hydrochlorination.

 Ruthenium and osmium in the form of their tetraoxides are distilled off from the solution obtained after hydrochlorination.

 Gold is precipitated from the resulting solution, bringing the redox potential (ORP) of any reducing agent to 500-550 mV (relative to the normal hydrogen electrode). Gold is recovered, precipitated and sent for processing.

 The solution after the extraction of gold contains platinum metals (PGM). However, it is contaminated with iron, lead, tin and other impurities of base metals.

 Purification of base metals is carried out by extraction with tributyl phosphate. In this case, the bulk of the PGM remains in the raffinate.

 Base metals reverse extracts also contain a small amount of PGM and, therefore, are not subject to discharge. PGM is isolated from them by electrolysis. Discharge solutions contain no more than 2 mg / l of PGM.

 The raffinate after separation of base metals is sent to the precipitation of ammonium chloroplatinate with ammonium chloride. Ammonium chloroplatinate is calcined, dissolved in hydrochloric acid and sent to the extraction of platinum.

 In the case where raw material is used as raw platinum or secondary raw materials, they are immediately sent to the extraction of platinum, bypassing the stage of precipitation of ammonium chloroplatinate.

 After separation of platinum, the reextract solution is purified from PGM by electrolysis on a fibrous cathode.

 Discharge solutions containing not more than 1 mg / l of PGM are sent to neutralization.

 The raffins of the platinum extraction processes obtained in the processing of raw materials of any kind are combined.

 In the event that palladium feed is subjected to processing, then after its dissolution, purification from gold and base impurities, palladium is extracted.

 The raffinate of this process is combined with the platinum extraction raffinate.

 The raffinate of the extraction process of platinum and / or palladium contains not more than 40% palladium and not less than 60% iridium and rhodium.

 From this solution, an PGM precipitate is isolated by electrolysis. The precipitate is chlorinated with chlorine in a sodium chloride melt, dissolved by hydrochlorination, i.e. treatment with chlorine in hydrochloric acid. Platinum and palladium are isolated from the solution by extraction. Rhodium and iridium remain in the raffinate. They are separated by extraction.

 Iridium goes into the organic phase, and rhodium remains in the raffinate.

 All insoluble residues resulting from the autopsy and / or cathodic precipitates obtained from solutions after extraction of the platinum group metals are dried, mixed with sodium chloride and chlorinated with chlorine. The resulting cinder is dissolved in hydrochloric acid in the presence of chlorine. The solution is purified from base metal impurities by extraction and the raffinate is sent to the extraction extraction of platinum and then palladium. The raffinate after extraction of palladium is sent to the separation of rhodium and iridium.

For this, iridium is oxidized to Ir ^IV , and rhodium remains in the trivalent state. Iridium is extracted into the organic phase, and rhodium remains in the aqueous phase. Iridium re-extract is purified from impurities by electrolysis. The presence of organic impurities remaining after extraction helps to increase the degree of purification. If there is little organics, it can be added to the solution additionally.

 Iridium and rhodium are isolated from solution in the form of metals or compounds.

 Separation of base metal impurities in the process head prior to the isolation of platinum, palladium, rhodium and iridium allows to obtain significantly cleaner products without additional purification operations, which in turn reduces the loss of platinum metals and reduces the number of mother liquors. The universality of the proposed invention is that, depending on the composition of the feedstock, you can choose the path of its opening or only hydrochlorination, or a combination of chlorination with hydrochlorination. The implementation of the chlorination process in conjunction with hydrochlorination allows you to open raw materials of any composition, including multicomponent oxysulfide raw materials.

 Extraction of platinum metals from the process head to the final product is Pt 94%, Pd 92%, Ir 82%, Rh 82%. The purity of the products obtained is not less than 99.96%. The number of stock solutions is reduced by 20%.

 Specific examples of the method are given below.

 Example 1

A) Platinum schlich in the amount of 100 kg is treated with 300 l of hydrochloric acid with a concentration of 300-350 g / l at t: W = 1: 3. The resulting pulp is heated to 80-90 ^o C and skip chlorine for 12-16 hours. Filtered. The concentration of platinum in the resulting solution is 180-200 g / l. This solution is directed to dehydration. The insoluble residue is again sent to dissolve.

B) The concentrate KP-1 in an amount of 100 kg is chlorinated with chlorine at 400 ^o C. Chlorides of arsenic, selenium, tellurium, tin, antimony, etc. turn into sublimates, and platinum metals remain in the cinder. Purification of platinum metals from impurities is 95%. The cinder is dissolved in hydrochloric acid with a concentration of 300-350 g / l at t: w = 1: 3. The resulting pulp is heated to 80-90 ^o C and skip chlorine for 5-6 hours. Filtered. The concentration of platinum in the resulting solution is 200 g / l, and palladium 40 g / l. The solution is sent to dehydration. If KP-1 is dissolved, bypassing the chlorination stage, then all impurities pass into the solution, which greatly complicates further processing. The dissolution time is 24-36 hours.

 Example 2

 To the solutions of Example 1A) and Example 1B) separately, but in parallel, i.e. sodium sulfite is added to each separately until reaching ORP = 500-550 mV. Gold is precipitated from solution. It is filtered off and sent for further processing. An anhydrous solution is obtained (solution 2A).

Then, ammonium chloroplatinate (HPA) is precipitated from solution 1B). To do this, add a solution of ammonium chloride with a concentration of 180-200 g / l with an excess of 20% of stoichiometry. HPA is filtered from the solution. The solution contains 120-140 g / l of palladium (solution 2B). HPA is calcined at 900-1000 ^o C for 4 hours. The resulting product was dissolved in concentrated hydrochloric acid at t: w = 1: 3. A platinum solution was obtained (solution 2B).

2A and 2B solutions were combined and purified by base metals impurities by extraction with tributyl phosphate (TBP) at V _o: V _in = 1: (5-7). The raffinate is a solution of platinum (3A) with a Pt content of 120 g / l, Pd 3 g / l, Ir 3 g / l, Rh 0.7-1 g / l.

 Solution 2B containing palladium is also purified from base metal impurities by extraction of their TBP similarly to the purification of platinum solutions. The raffinate is a solution of palladium (3B) containing Pd 110-120 g / l, Pt 1-2 g / l, Ir 0.1 g / l, Rh 0.5 g / l.

Platinum solution (3A) was isolated by extraction with TBP platinum at V _o: V _B = 1.6: 1. The back-extraction is conducted with water at V _o: V _in = 1: 1. Pf 0.1 g / L, Pd 2 g / L, Ir 2 g / L, Rh 0.5 g / L remain in the raffinate.

 Reextract contains Pt 70 g / L, Pd 10 mg / L, Ir and Rh traces. Platinum is extracted from the stripping by any known method.

Palladium is extracted from a solution of palladium (3B) with petroleum sulfoxides at V _o : V _in = 4: 1. Reextraction is carried out with a solution of sodium chloride at V _o : V _in = 1: 0.3. Reextract contains, Pd 35 g / l, Pt less than 10 mg / l, Ir and Rh traces. It is sent to the extraction of palladium.

 The raffinate contains Pt 0.5-0.7 g / L, Pd 200 mg / L, Ir 0.05 g / L, Rh 0.2 g / L.

 The raffinate obtained by extraction of platinum from solution 3A and the raffinate obtained by extraction of palladium from solution 3B are combined. The combined solution is sent to the electrochemical extraction of PM on a fibrous cathode according to known technology.

 The mother liquors obtained after isolation of platinum and palladium are also sent to the electrochemical isolation of PM.

All the obtained cathodic precipitates are combined with insoluble sediments of schlich platinum and KP-1 and subjected to chlorination in a melt of sodium chloride at 700-800 ^o With a ratio of sodium chloride to precipitate 3: 1 for 3 hours.

The cinder is dissolved in 20 g / l hydrochloric acid at t: W = 1: 4. The solution contains Pt 20 g / L, Pd 40 g / L, Ir 50 g / L, Rh 10-15 g / L. From this it was extracted with platinum and palladium via TFB when V _o: V _in = 2: 1. The re-extract is directed to the extraction of platinum and palladium. The raffinate contains Ir 40 g / l, Rh 10 g / l and is an iridium-rhodium concentrate. The solution is nitrated with sodium nitrite NaNO ₂ and precipitated by adding ammonium chloride, insoluble nitrite salts of iridium and rhodium. They are dissolved in concentrated hydrochloric acid, obtaining a pure concentrated solution of iridium and rhodium. Iridium is oxidized to the tetravalent state and its TBP is extracted. Rhodium remains in the raffinate. The extraction of iridium and rhodium from solutions is carried out by any known method. Before extracting iridium, the solution is subjected to electrochemical purification at a cathodic current density of 15-40 A / dm ² in the presence of organic substances: tributyl phosphate, and / or sulfoxides, and / or kerosene, and / or octanol.

 The presented example shows that only this sequence of operations, the combination of extraction and electrolysis, allows complex processing of raw materials of platinum metals with their separation and purification with high recovery without the formation of mother liquors.

Claims (5)

 1. The method of extraction and separation of platinum group metals, including opening the feedstock by hydrochlorination, gold separation, extraction purification from base metal impurities, palladium extraction and platinum extraction, obtaining iridium and rhodium concentrate and their separation by extraction, characterized in that the gold is separated, bringing the redox potential of the solution to 500-550 mV with respect to the normal hydrogen electrode, from the solution obtained after purification from impurities of base metals Allov, platinum and / or palladium are extracted by extraction in parallel, but separately, with the formation of separate extracts of platinum and / or palladium, then platinum and / or palladium are separately extracted from the extracts, the raffinates obtained by platinum extraction and / or palladium extraction are combined and precipitate from them a precipitate of platinum metals by electrolysis at the cathode, the cathode precipitate is dissolved, platinum and palladium are isolated from the solution to obtain a concentrate of iridium and rhodium.  2. The method according to p. 1, characterized in that prior to hydrochlorination, chlorination is carried out to produce sublimates of impurities, osmium and ruthenium and a cinder containing platinum group metals.  3. The method according to p. 1 or 2, characterized in that oxide-sulfide concentrates of platinum metals are used as the starting material, ammonium chloroplatinate is precipitated from the solution after separation of gold, it is dissolved and the resulting solution is sent for purification from base metal impurities.  4. The method according to p. 1, or 2, or 3, characterized in that the insoluble hydrochlorination residue and / or cathode precipitates obtained from solutions after extraction of the platinum group metals are chlorinated with chlorine in a melt of chloride salts, the cinder is dissolved in hydrochloric acid, the resulting solution is purified from non-base metal impurities by extraction, platinum is extracted from the purified solution by extraction, and then palladium, and iridium and rhodium are separated from the obtained raffinate by extraction.  5. The method according to p. 4, characterized in that the iridium reextract obtained as a result of extraction separation of iridium and rhodium is subjected to electrochemical purification in the presence of organic substances: tributyl phosphate and / or sulfoxides and / or kerosene and / or octanol.