RU2391419C1 - Processing method for platinum-group metal concentrates based on iron and nickel for platinum-group metal recovery - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention refers to noble metal metallurgy and can be applied in processing technology for platinum-group metal concentrate based on iron and nickel. Processing method for platinum-group metal concentrates on iron and nickel base for platinum-group metal recovery includes concentrate processing with hydrochloric acid with transition of platinum-group metals to solution. Further insoluble sediment is separated, solution is treated with sodium nitrite, and iron hydroxide sediment is removed. Before processing with hydrochloride acid, the concentrate is repulped in water, the pulp is heated, nitric acid is added in amount required for dissolution of about 60% of iron and nickel, and the pulp is heated for 4-5 hours at 85-100C. Hydrochloric acid processing involves addition of hydrochloric acid in amount required for dissolution of remaining iron, nickel and platinum-group metals and heating for 4-5 hours more at 85-100C. Phosphoric acid or sodium phosphate is added to the solution before sodium nitrite treatment. ^ EFFECT: deep recovery of concentrate, prevented formation of explosive air and hydrogen mix and extremely poisonous phosphine gas (PH3). ^ 1 tbl, 1 ex

Description

The invention relates to the metallurgy of precious metals (BM) and can be used in the processing technology of the concentrate of platinum metals on an iron-Nickel basis.

Concentrates of this type can be formed during the processing of spent automotive catalysts by pyrometallurgical methods, followed by grinding. Their composition differs significantly, which is associated both with different types of products supplied to concentrating smelting, and with the features of the technologies used. The main components of the concentrates are: iron - the mass fraction of which is (25-50)%, nickel (5-20)%, phosphorus (2-10)%, silicon (5-20)%, titanium (1-2)%. Of the platinum metals, as a rule, there are: platinum (3-5)%, palladium (3-5)% and rhodium (0.5-1.0)%.

The initial stage of the processing of any concentrates of platinum metals is their dissolution. In this case, there are often problems of a diverse nature. In some cases, they are associated with low activity of raw materials. In others, on the contrary, with the rapid course of the process, accompanied by the release of harmful and dangerous substances. One of the most common and most commonly used methods in practice is the dissolution of platinum metal concentrates in acidic media during oxidation.

A known method of processing concentrates of platinum metals, including hydrochlorination in hydrochloric acid when heated, separating the insoluble precipitate, processing the resulting solution with sodium nitrite (nitration), separating the precipitate and subsequent extraction from the solution of platinum metals by known methods [1]. This method is the closest in technical essence to the claimed method and adopted as a prototype.

The main disadvantages of the prototype method when it is used in the processing of platinum metal concentrates on an iron-nickel basis for the extraction of platinum metals include: the allocation of explosive hydrogen during the interaction of iron with hydrochloric acid; the formation of a highly toxic chemical compound phosphine, the maximum permissible concentration of which in air is 0.1 mg / m ³ ; long duration of the process of dissolution of the concentrate; unproductive oxidant consumption due to the low activity of the concentrate; the formation of difficult to filter pulp, which requires the use of sophisticated filtering equipment.

The technical result, which is achieved by the proposed method of processing platinum metal concentrate on an iron-nickel basis for the extraction of platinum metals, consists in using a combination of such hydrometallurgical processing methods that allow platinum metals to be sufficiently completely transferred to the solution and, at the same time, do not have the listed the disadvantages inherent in the prototype method.

The desired technical result is achieved by the fact that in the known method of processing platinum metal concentrates on an iron-nickel basis for the extraction of platinum metals, which includes treating the concentrate with hydrochloric acid with the conversion of platinum metals into a solution, separating the insoluble residue, treating the solution with sodium nitrite and separating the precipitate of iron hydroxide, Before treating the concentrate with hydrochloric acid, it is pulped in water, the pulp is heated, nitric acid is introduced in the volume necessary for dissolving 60% of iron and nickel, and heated for 4-5 hours at a temperature of (85-100) ° С, hydrochloric acid treatment is carried out by adding hydrochloric acid in the amount necessary to dissolve the remaining part of iron and nickel and platinum metals, and heated for 4-5 hours at a temperature of (85-100) ° C, and before the solution is treated with sodium nitrite, phosphoric acid or its sodium salt is introduced into it.

The essence of the proposed method is as follows. In the concentrate, part of the iron is in the form of phosphide (Fe ₃ P). In nitric acid, phosphorus is oxidized and passes into solution in the form of phosphoric acid. Thus, the possibility of the formation of an explosive air-hydrogen mixture and a highly toxic phosphine gas (PH ₃ ) is excluded. When the starting product is dissolved in nitric acid, most of the iron, nickel, as well as up to 10% platinum and palladium and up to 30% rhodium pass into the solution. The consumption of nitric acid depends on the composition of the feedstock and is selected so that it is sufficient to dissolve approximately 60% of iron and nickel (see reaction 1). Since this type of concentrate does not have high activity, after the introduction of nitric acid, the pulp should be warmed up at a temperature of (85-100) ° С. Special experiments have shown that to complete the process, it is necessary to carry out heating for 4-5 hours. With a shorter heat treatment time, the dissolution process does not have time to complete, and longer heating does not lead to a significant increase in the dissolution completeness. The indicated temperature is the most optimal. At lower temperatures, to complete the dissolution process, it is necessary to increase the duration of heating, and at temperatures above 100 ° C, boiling occurs, accompanied by foaming and possible ejection of pulp from the reaction apparatus. The oxidation of iron and nickel consumes only half of the introduced nitric acid. Another part is used for the formation of nitrate salts:

With the subsequent introduction of hydrochloric acid, iron nitrate acts as an oxidizing agent in the reaction of dissolution of the remaining part of iron, nickel, and also platinum metals:

The consumption of hydrochloric acid also depends on the composition of the feedstock and is calculated by reactions 1-4. The temperature and time parameters were chosen for the same reasons as when dissolving in nitric acid.

The resulting solution, in addition to platinum metals, contains up to 80 g / l of iron. To separate the iron and the subsequent separation of platinum metals, the solution is treated with sodium nitrite. In this case, iron is hydrolyzed and precipitates in the form of hydroxide. It is known from the practice of the process that iron hydroxides are slowly filtered and, in addition, adsorb platinum metals on themselves. In order to eliminate the aforementioned negative phenomena, it is proposed to introduce phosphoric acid or its sodium salt into the solution before treatment with sodium nitrite. The phosphate ion is introduced in order to isolate from the iron solution not in the form of hydroxides, but in the form of phosphate. The practice of the process showed that iron phosphate is much better filtered and washed from the mother liquor containing platinum metals than its hydroxide. The consumption of phosphoric acid or its sodium salt also depends on the concentration of iron in the solution supplied to the treatment with sodium nitrite.

EXAMPLE 1

100 ml of water was poured into a glass reactor, a stirrer was turned on, and 100 g of concentrate of the following composition was loaded,%: Fe - 45, Ni - 15, P - 6, Pt - 4.6, Pd - 4.8, Rh - 0.9 , Si - 16. The pulp was heated to a certain temperature and 300 ml of nitric acid were slowly added, after that, with constant stirring, an isothermal exposure was carried out at a given temperature for the allotted time. Then 350 ml of hydrochloric acid was slowly introduced into the pulp and isothermal exposure was also carried out for a certain time at a given temperature. The pulp was filtered, the insoluble residue was washed, the resulting solutions were combined, the volume was determined and analyzed by emission-coupled plasma (ICP). The insoluble residue was dried, weighed and the mass fraction of platinum metals was determined in it by spectral method. Received 700 ml of a solution of the following composition, g / l: Fe - 57 g / l; Ni - 18 g / l; Pt - 6.4 g / l; Pd - 6.7 g / l; Rh - 1 g / l. Considering that the bulk of the phosphorus in the concentrate turned into phosphoric acid, before processing with sodium nitrite, not 47 ml of concentrated H ₃ PO ₄ solution was added to the solution, which is necessary to precipitate all the iron in the form of phosphate, but only 37 ml. The resulting solution was treated with sodium nitrite when heated, the pulp was warmed and filtered. The precipitate was washed with water, the basic nitrite solution and the promoters were combined, the volume was determined and analyzed by emission-coupled plasma (ICP). The precipitate was dried, weighed, and the mass fraction of platinum metals was determined in it by a spectral method. Similar experiments were carried out with the same initial concentrate at different temperatures and duration of exposure. The results are presented in table 1.

Table 1. The distribution of metals upon dissolution of iron-nickel-based PGM concentrate.

Experience number Product Name τ warming up, hour T warming, ° C V ml
M, g Distribution% HNO ₃ Hcl HNO ₃ Hcl Pt Pd Rh Fe Ni one N. Residue from dissolution four four 90 90 eighteen 1.8 1.5 17.6 twenty 26.7 Nitrite solution 700 97.7 97.9 78.7 2.0 71 N. nitrate residue 108 0.5 0.6 3.7 78 2.3 2 N. Residue from dissolution one four 90 90 24 5.1 4.2 30.6 39 42.3 Nitrite solution 700 94.5 95.3 66.1 1.6 55.7 N. nitrate residue 97 0.4 0.5 3.3 59.4 2.0 3 N. Residue from dissolution four one 90 90 35 46.8 34.4 54.8 45.6 47.1 Nitrite solution 700 52.8 65.2 42.1 1.2 51.2 N. nitrate residue 84 0.4 0.4 3.1 53.2 1.7 four N. Residue from dissolution four four fifty 90 27 7.3 5.9 33.4 36 45.1 Nitrite solution 700 92.3 93.7 63.1 1.5 52.9 N. nitrate residue 93 0.4 0.4 3.5 62.5 2.0 5 N. Residue from dissolution four four 90 fifty 32 49.3 37.7 56.4 43.4 47.1 Nitrite solution 700 50.4 61.9 40.3 1.4 50.8 N. nitrate residue 85 0.3 0.4 3.3 55.2 2.1

Thus, the proposed method for the processing of iron-nickel-based platinum metal concentrates to extract platinum metals allows their high extraction to be achieved, eliminating the formation of an explosive air-hydrogen mixture and the release of a highly toxic gas - phosphine. The resulting insoluble residues with a low content of platinum metals can be sent to enrichment operations using known technologies.

Information sources

1. Yu.A. Kotlyar, M.A. Meretukov, L.S. Strizhko. Metallurgy of precious metals. T.2. Tutorial. M., Publishing House "Ore and Metals", 2005, p. 269-273.

Claims (1)

A method of processing iron-nickel-based platinum metal concentrates to extract platinum metals, comprising treating the concentrate with hydrochloric acid with the conversion of platinum metals into a solution, separating the insoluble residue, treating the solution with sodium nitrite and separating the precipitate of iron hydroxide, characterized in that it is pulped before the concentrate is treated with hydrochloric acid in water, the pulp is heated, nitric acid is introduced in the amount necessary to dissolve about 60% of iron and nickel, and warmed up for 4-5 hours at a temperature of 85-100 ° C, treatment with hydrochloric acid is carried out by adding hydrochloric acid in the amount necessary to dissolve the remaining part of iron and nickel and platinum metals, and heated for another 4-5 hours at a temperature of 85-100 ° C, and before the solution is treated with sodium nitrite, phosphoric acid or its sodium salt is introduced into it.