Hydrometallurgy

Pressure Oxidation (POX):

• Refractory gold ore is fed into an autoclave

• Ore oxidized under high pressure and temperature

• Oxygen is injected to break down sulfide minerals

• Liberates gold from sulfide matrix

Neutralization:

• Acidic POX discharge is neutralized, often with lime

Carbon-in-Leach (CIL):

• Neutralized slurry fed into CIL circuit

• Cyanide added to dissolve gold

• Activated carbon added to adsorb dissolved gold

• Multiple tanks in series for leaching and adsorption

Carbon handling:

• Loaded carbon separated and sent for elution (stripping)

• Gold recovered from strip solution by electrowinning

Tailings disposal:

• Barren slurry from CIL sent to tailings storage facility

Ore Preparation:

• Crushing and sometimes agglomeration of ore

• Stacking on prepared leach pad

Leaching:

• Cyanide solution sprayed or dripped onto ore heap

• Solution percolates through heap, dissolving gold

Solution Collection:

• Pregnant leach solution (PLS) collected at base of heap

Carbon-in-Column (CIC):

• PLS pumped through a series of columns containing activated carbon

• Dissolved gold adsorbs onto carbon

• Barren solution recycled back to heap

Carbon Handling:

• Loaded carbon periodically removed from columns

• Sent for elution (stripping) and regeneration

Gold Recovery:

• Gold recovered from strip solution by electrowinning

• Smelting of cathodes to produce doré

Solution Management:

• Ongoing monitoring and adjustment of cyanide levels and pH