Gold Process Comparison – Neomet Technologies

Although primarily conceived as an alternative to the use of cyanidation for refractory and carbonaceous ores and concentrates, the Neomet Gold Process has a number of advantages.

Operation	Pressure Oxidation (POX)	Bacterial Leaching	Roasting	Albion/ Activox	Nitric Acid	Neomet Chloride
Feed	Concentrate	Concentrate	Ore or Concentrate	Concentrate, ultra fine grind	Concentrate	Ore or Concentrate
Arsenic	Type II mineral, ferrihydrite finish, stable	Ferrihydrite, stable only if sufficient Fe in solution at time of precipitation	Arsenic trioxide, separate treatment plant required plus separate source of iron to make stable residue	Ferrihydrite, stable only if sufficient Fe in solution at time of precipitation	Scorodite, ferrihydrite finish, stable	Scorodite, no finish necessary
Residue disposal	Dedicated area, non-reducing	Dedicated area, non-reducing	Dedicated area, non-reducing	Dedicated area, non-reducing	Dedicated area, non-reducing	Dedicated area, non-reducing
Effluent issues	None if no K or Na dissolves	Bacteria cultures leaking into water table	Weak acid from scrubbers or acid plant	None if no K or Na dissolves	Nitrates leaking into environment	Chlorides into environment. However, wash efficiency so high, that such is minimal
Alkali metals	Potential to form KOH and NaOH on lime neutralization, which will slowly decompose As minerals. Potential to form jarosites, consuming acid and iron.	Potential to form KOH and NaOH on lime neutralization, which will slowly decompose As solids. Potential to form jarosites, consuming acid and iron.	No issues	Potential to form KOH and NaOH on lime neutralization, which will slowly decompose As solids. Potential to form jarosites, consuming acid.	Potential to form KOH and NaOH on lime neutralization, which will slowly decompose As minerals. Potential to form jarosites, consuming iron, but helping control sulphate balance.	K and Na separated, chloride recovered. Not mixed with As solids, therefore no impact.
Aluminium	Forms alunites, consumes acid, scaling issues	Will dissolve, consumes acid and lime	No issues	Will dissolve, consumes acid and lime	Will dissolve, consumes acid and lime	Dissolves, recovered with hematite. Can be recovered as alumina if sufficient present
Gold recovery	Cyanide in separate leach circuit, requires cyanide destruction. Long residence time (24-96 hours)	Cyanide in separate leach circuit, requires cyanide destruction. Long residence time (24-96 hours)	Cyanide in separate leach circuit, requires cyanide destruction. Long residence time (24-96 hours)	Cyanide in separate leach circuit, requires cyanide destruction. Long residence time (24-96 hours)	Cyanide in separate leach circuit, requires cyanide destruction. Long residence time (24-96 hours)	Direct from chloride leach as pure gold. Rapid turnaround time
Silver recovery	Along with gold as doré metal	Along with gold as doré metal	Along with gold as doré metal	Along with gold as doré metal	Along with gold as doré metal	Separately as pure silver or together with gold.
By-products	None	None	None	None	None	Can recover any PGMs, Ga, Sc, etc.