Recovery of Gold from Ores.
U S Pat 3 764 650 1973 Oct; :
Gold is extracted from oxidized and carbonaceous ores (65-200 mesh) by forming an aqueous slurry with a soluble chloride such as that of k, na, ca, or mg providing chloride ion in a concentration equivalent to that from 5-20 pct nacl, adjusting the ph to 0.5-1.8 With hcl, hno3, or h2so4, and bubbling ozone through it for 4-16 h at 23 deg-25 deg. C with 20-40 lb o3 consumed/ton of ore. When this was done with 100 g of ore containing 0.4 Oz au/ton and 10 g nacl in 200 ml of h2o at ph 1 by bubbling o3 for 8 h, the au recovery in solution was 95 pct. The chloride solution can be used repeatedly with o3 on more ore until the chloride concentration becomes too low.
U.S. Pat. 3,764,650; Oct. 9, 1973; Chem. Abstr. 80:29,439N