Comparative Leaching of Gold and Silver Ores With Cyanide and Thiourea Solution.
Paper in Precious Metals '89 Miner Mat and Mater Soc 1988 :253-259
There is currently much interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using alkaline cyanide solution. Agitation leaching tests were performed by the U.S. Bureau of Mines on 14 precious metal ores using sodium cyanide (nacn) and thiourea [(nh2)2cs] as extractants. The objective was to compare the results of the two extractants. Nacn was used at a concentration of 2 g/l with and without h2o2 as an oxidant. (Nh2)2cs was used at concentrations of 2 and 20 g/l, and the solution potential was controlled at 390 to 420 mv standard hydrogen electrode (eh) with fe2(so4)3. With both reagents at 2 g/l extractant levels, nacn extracted more gold and silver than (nh2)2cs from all of the ores. At 20 g/l (nh2)2cs compared with 2 g/l nacn, (nh2)2cs extracted more gold than nacn from two ores, the same amount from one ore, and more silver from one ore. Nacn extracted more gold than (nh2)2cs from 10 ores and more silver from 4 ores.
Paper in Precious Metals '89; Miner., Mat., and Mater. Soc., 1988, PP. 253-259