CIL/CIP Carbon Selection in Gold Mining: Hardness, Gold Loading and Attrition Loss

In gold mining, carbon-in-leach (CIL) and carbon-in-pulp (CIP) processes use high-quality activated carbon to recover gold from the loaded solution. Coconut-shell-based granular carbon is generally preferred. Carbon selection revolves around three core metrics that often conflict with one another.

1. Hardness (Attrition Resistance)

CIL/CIP tanks are continuously agitated and the carbon is pumped between screens. This mechanical stress abrades soft carbon into fines. High hardness (typically high ball-pan hardness) reduces fines formation. Fines are critical because gold-loaded fine carbon can pass through the screens and go to tailings — a direct gold loss.

2. Gold Loading Capacity and Kinetics

How fast and how much gold-cyanide complex the carbon can hold (activity / K-value) determines the number of tanks and the carbon inventory. High activity means higher recovery with less carbon. However, very high activity can sometimes come with a more porous/softer structure, so activity is never assessed alone.

3. Attrition Loss and Total Cost

Attrition loss directly affects both the carbon replacement cost and the fines-related gold loss. The right choice is not the highest activity, but the carbon that balances sufficient activity with high hardness. The evaluation should be made on total cost of ownership (carbon + gold loss + regeneration).

Selection Checklist

• Hardness / attrition resistance — the highest achievable value.
• Activity (gold loading) — a level that meets the process target.
• Particle size — typically 6×12 mesh; screen compatibility.
• Ash and platelet content — low impurities.
• Wettability and re-activation ability — regeneration performance.