CIL vs CIP: Choosing the Right Gold Recovery Process
Key takeaways
- Both processes use activated carbon to adsorb dissolved gold; the difference is whether leaching and adsorption share the same tanks.
- CIL is the modern default. Adsorbing gold as it dissolves suppresses losses and handles ore with naturally occurring carbon better.
- CIP can be simpler to operate and is well suited to clean, fast-leaching free-milling ore.
- Ore with carbonaceous matter points to CIL, because carbon in the pulp competes for dissolved gold.
- Test work, not preference, decides. Leach kinetics and preg-robbing behaviour determine which circuit recovers more.
CIL and CIP are the two standard ways to recover gold from a cyanide leach, and they are frequently confused because both use activated carbon and both end with loaded carbon going to an elution circuit. The distinction is simple once you see it, but it has real consequences for recovery, tank design and operating complexity.
The difference in one sentence
In CIP (carbon-in-pulp), leaching and adsorption happen in separate stages: the ore is leached in a series of tanks, then the pulp is passed to a second series of tanks where activated carbon adsorbs the dissolved gold. In CIL (carbon-in-leach), carbon is added directly to the leach tanks, so gold is adsorbed at the same moment it dissolves.
| Factor | CIL (carbon-in-leach) | CIP (carbon-in-pulp) |
|---|---|---|
| Leaching and adsorption | Same tanks, simultaneous | Separate tanks, sequential |
| Tank count | Fewer — one combined train | More — leach train plus adsorption train |
| Handles preg-robbing carbon | Better — gold is captured before native carbon can adsorb it | Weaker — native carbon competes |
| Suits fast-leaching ore | Yes | Yes |
| Suits slow-leaching ore | Generally preferred | Requires longer leach train |
| Operating complexity | Carbon management in leach tanks | Simpler per tank, more tanks |
Why CIL became the default
Three advantages explain why CIL has become the more common choice, particularly on new projects.
First, it suppresses losses. Once gold is in solution it can be lost again — adsorbed by naturally occurring carbon in the ore, or precipitated back onto sulphide surfaces. In CIL, activated carbon is present throughout the leach, so dissolved gold is captured almost as soon as it enters solution, before those competing reactions can take it.
Second, it handles carbonaceous ore. Ore containing graphitic or organic carbon is a serious problem for CIP, because the native carbon adsorbs gold just as activated carbon does — but that gold is lost with the tailing instead of being harvested. In CIL, the activated carbon in the leach tanks competes successfully with the native carbon and captures most of the gold first.
Third, it often needs fewer tanks. Because leaching and adsorption are combined, a CIL train can be shorter than the equivalent leach-plus-adsorption CIP arrangement, which reduces capital cost and footprint.
When CIP still makes sense
CIP remains a sound choice for clean, free-milling ore that leaches quickly and contains no native carbon. Because the leach train and the adsorption train are separate, each can be optimized independently — the leach for dissolution kinetics, the adsorption train for carbon concentration and transfer rates.
Some operators also find CIP easier to control. Carbon is only present in dedicated adsorption tanks, so carbon inventory, screening and transfer are confined to a known part of the circuit. Where ore is simple and capital is tight, that simplicity can outweigh CIL’s recovery advantage.
What actually decides the choice
The decision should follow lab and pilot test work, not preference. Three tests matter most. A leach kinetics test establishes how fast the gold dissolves and how much residence time the leach needs. A preg-robbing test measures how much dissolved gold the ore’s own carbon adsorbs — a high figure strongly favours CIL. And a carbon activity test confirms that activated carbon will perform as expected in the circuit.
Where the ore is clean and fast-leaching, the two circuits usually perform comparably, and capital and operating cost decide. Where the ore is carbonaceous or leaches slowly, CIL generally wins on recovery, and that recovery difference usually outweighs the cost of the extra carbon handling.
Both routes then share the same downstream steps: loaded carbon is stripped in an elution circuit and the gold recovered by electrowinning. You can review the equipment for both in our gold CIP/CIL equipment range.
Rule of thumb: clean, fast-leaching ore — either circuit will work, and cost decides. Carbonaceous, slow-leaching or preg-robbing ore — choose CIL.
Frequently asked questions
What is the main difference between CIL and CIP?
In CIP, leaching and carbon adsorption happen in separate tank trains. In CIL, activated carbon is added directly to the leach tanks, so the gold is adsorbed at the same time it dissolves. CIL is generally preferred for ore containing natural carbon.
Which gives higher gold recovery, CIL or CIP?
CIL generally gives slightly higher recovery, particularly on ore containing carbonaceous matter or ore that leaches slowly, because dissolved gold is captured before competing reactions can remove it. On clean free-milling ore the two are often comparable.
Why does CIL handle carbonaceous ore better?
Because graphitic or organic carbon in the ore adsorbs dissolved gold, and in a CIP circuit that gold is lost with the tailing. In CIL, activated carbon is already present in the leach tanks and captures most of the gold before the native carbon can take it.
How many tanks does a CIL circuit need?
It depends on leach kinetics and the required residence time, but CIL circuits often need fewer tanks overall than an equivalent CIP arrangement, because leaching and adsorption are combined in the same train.
Can an existing CIP plant be converted to CIL?
Often yes, by introducing carbon into the leach tanks and adjusting carbon handling and screening. The conversion is not always straightforward, and it should be assessed against test work showing a genuine recovery benefit.
Deciding between CIL and CIP? Send us your leach and preg-robbing test results and we will recommend the circuit.
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