Technical Details

Alkaline/ammonia leach
Proprietary two stage leaching process
- Ore specific cure/pre-treatment stage
- Heap or tank leaching
Proprietary solvent extraction step to avoid ammonia carry-over into solvent
Uses conventional equipment
- Electro-winning is identical to conventional acid circuits
- Replacement acid leach in current operations
- Minimal changes to plant
- Higher organic transfer efficiencies requires smaller plant
Environmental benefits – a ‘green’ process for a ‘green’ metal:
- Reduced transport/shipping impact and costs
- Minimal likelihood of AMD

AmmLeach® - Advantages I

Parameter	Acid	AmmLeach™
Mineralogy	Oxides, carbonates, silicates, some sulphides	Almost any – dependant upon curing stage
Curing	Concentrated H 2 SO 4	Tailored to ore mineralogy
Selectivity	Low- iron, manganese, calcium and silica are likely problems	High- no iron, manganese, calcium or silica dissolution
Rate of extraction	Limited by acid strength and diffusion	Ammonia concentration in leach solution matched to leaching rate
Recovery	80% of leachable	70-80% in 130 days typical
Heap lifetime	55-480 days	~80-130 days typical
Sulphate precipitation	Reduced permeability in heap, break down of clays and plant scaling due to precipitation of gypsum and jarosite	Calcium and iron solubilities too low for precipitation, also low sulphate levels in leach solution

Parameter	Acid	AmmLeach™
Leachate consumption	Depends upon carbonate content 3.7-27 kg/t reported	Depends on concentration used, field trials show less than 1kg/t
Safety	Concentrated acid required	Gaseous ammonia main hazard, on ‑ demand systems using hydrolysis of urea minimise transport risks
Precious metals	Heap to be neutralised before cyanidation	Neutralisation not required, potential for simultaneous recovery using thiosulphate or sequential leaching using cyanide
Mine closure	Heap requires washing, neutralisation and long term monitoring to avoid AMD	Heap can be washed and left, residual ammonia acts as fertiliser for vegetation regrowth, minimal likelihood of AMD.