METHOD OF EXTRACTION OF NOBLE METALS, MAINLY GOLD FROM SOLUTIONS Russian patent published in 2003 - IPC

FIELD: hydrometallurgy of noble metals; extraction of noble metals, gold in particular from solutions containing active chlorine of underground and heap leaching and galvanic runoffs. SUBSTANCE: proposed method includes clarification of solution, precipitation of gold by changing oxidation reduction potential of productive solution below region of location of metal being extracted in dissolved state, removal and processing of gold-containing sediment. Precipitation of gold is performed at pH below or equal to 3; change of oxidation reduction potential is performed by blowing-off, application of energy of ultrasonic oscillations, evacuation, heating and introduction of reductants or combination of said procedures together with entrapping gaseous chlorine and its utilization; pH of productive solution directed for precipitation of gold exceeds 3; it is preliminarily slightly oxidized with hydrochloric acid to pH lesser than or equal to 3. Used as reductants are reagents selected from the following series: hydrazine, formaldehyde, formic acid and its salts, sulfur dioxide, sulfites, thiosulfate, solutions of salts of thermally unstable metals in lowest degree of oxidation as well as byproduct of production of saltpeter ammonium sulfite-bisulfite. Sediment is removed by filtration of solution by use of built-up layer of filtering powder from perlite, diatomite, kieselguhr or tripolite. EFFECT: high degree of extraction of gold from acid, neutral and alkali solutions containing active chlorine; enhanced ecological safety. 3 cl, 4 tbl, 4 ex