METHOD OF RECOVERY OF PLATINUM METALS FROM SLIMES Russian patent published in 2001 - IPC

FIELD: hydrometallurgy of noble metals; applicable in recovery of platinum metals from slimes formed in production of nitric acid. SUBSTANCE: method includes leaching of slimes conducted in two stages with separation of solution and cake washing after each stage. The first stage of leashing is carried out in hydrochloric acid, and the second stage is carried out in mixture of concentrated hydrochloric and nitric acids. Cake after the first stage of leaching is roasted at temperature of 800-900 C for 1 h and directed to the second stage of leaching. Solutions and washings waters of both stages are combined, corrected by content of platinum metals up to 5-50 g/l, and platinum metals are recovered by precipitation with produced precipitate which is roasted and melted into ingot. Leaching is carried out at temperature of 80-90 C. Platinum metals are precipitated from solution depending on content of platinoids in it using the following method: with hemp of hydrazine at pH 2-4 and temperature of 70-80 C to obtain collective concentrate of platinum metals; with ammonium chloride at pH not above 2 and temperature within 40 C to obtain ammonium chloroplatinate; and precipitation with use of electrolysis. EFFECT: considerable increase of recovery degree of platinum metals from slimes due to optima sequence and combination of technological procedures ensuring practically full transition of platinoids into solution in leaching. 6 cl, 1 tbl, 4 ex