9303841 Han This is an examination of an alternative approach to the extraction of precious metals from refractory ores; the approach is intended to pose a much lesser threat to environmental quality than the presently predominant cyanide leaching process. The dissolution mechanism of gold in ammoniacal solution at elevated temperature and pressure is studied. Unique features of the approach include use of relatively high temperature and pressure in an autoclave, use of oxygen to regenerate the copper or cobalt oxidant, and measurement of electrochemical potentials at high temperature in an autoclave modified for this purpose. The oxidation of sulfide in ammoniacal solution is also investigated. If fully successful, this effort should result in a process that would pose a much lesser environmental problem than current technology, and would also permit extraction of gold (and maybe silver) from ores presently considered refractory.
