CIP (Carbon-in-Pulp) and CIL (Carbon-in-Leach) are both agitated-cyanide milling-circuit gold recovery methods. The difference: CIP leaches the ore in a separate tank circuit and then transfers slurry to a downstream carbon-adsorption circuit, while CIL combines leach and carbon adsorption in the same tanks. CIL is simpler and more common in modern plants; CIP is preferred when leach kinetics are very slow or when the carbon is sensitive to leach-tank conditions.
CIL — Carbon-in-Leach
Activated carbon is added directly into the leach tanks alongside the cyanide solution. Gold dissolves and is immediately adsorbed onto the carbon — single-pass through one tank train. Simpler flowsheet, fewer pumps, lower CapEx. Most modern gold mills are CIL.
CIP — Carbon-in-Pulp
Leach in a separate tank train first; then transfer the leached slurry to a downstream carbon adsorption train. The advantage: longer leach residence time without carbon contact (helpful for slow-leach ores), and carbon contacts a slurry with already-elevated gold concentration (potentially higher loading).
Decision Factors
Choose CIL when leach kinetics are fast (most heap-amenable ores), capital budget is tight, and operating complexity should be minimized. Choose CIP when leach is slow (refractory or partially-refractory ores), when carbon abrasion in leach tanks is a problem, or when separating the leach and adsorption circuits gives better metallurgical control.
The KCA Reference
KCA has delivered both CIP and CIL plants at scales from 1 t/d pilot (Peru and Bolivia) to 20,000 TPD industrial (San Martin, Honduras). Full detail on our CIP/CIL Plant Design reference.
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