Gold CIL vs CIP: Choosing the Right Leaching Route

CIL and CIP: two cyanidation routes, one recovery goal

Carbon-in-leach (CIL) and carbon-in-pulp (CIP) are the two standard activated-carbon routes for recovering gold from finely ground ore. The cil vs cip decision affects every major tank on the site, so you make it early. Both processes dissolve gold in an alkaline cyanide solution, then collect the dissolved gold on activated carbon. On suitable ores, gold recovery can reach 99%. The difference between the two routes is arrangement: CIP leaches first and adsorbs second; CIL runs both steps in the same vessel.

This distinction drives how much carbon you move, how many tanks you install, and how your pumps and screens are arranged. The choice is not about whether cyanidation works. It is about which flow sheet lets your particular ore release gold efficiently enough to justify the capital and operating cost.

How carbon-in-pulp (CIP) works

Carbon-in-pulp refers to a two-stage cyanidation flow sheet. In the first stage, ground slurry is leached in dedicated agitation tanks until gold dissolves into solution. The slurry then moves to a separate train of adsorption tanks, where activated carbon contacts the pregnant solution and takes up the dissolved gold. Because leaching and adsorption are separated, you can size each train independently. You can run the leach circuit at the residence time the ore needs, while the carbon circuit runs at a different carbon concentration and transfer schedule.

CIP often suits ores that leach quickly. If most of the gold is in solution after the first few tanks, there is little benefit to adding carbon early. Keeping carbon out of the leach tanks also reduces carbon abrasion and the amount of carbon that has to be screened, pumped and regenerated. A fast-leaching ore in a CIP plant can be simpler to operate because the carbon inventory is confined to the adsorption section.

Xinhai has delivered CIP plants where this separation makes sense. For example, its published project list includes a 4,000 t/d gold carbon-in-pulp plant in Kyrgyzstan. A plant of that scale typically uses multiple leach tanks ahead of a carbon train, but the exact tank count follows laboratory kinetics rather than a fixed template.

How carbon-in-leach (CIL) works

Carbon-in-leach, or CIL, refers to a single-stage arrangement in which cyanide leaching and carbon adsorption happen simultaneously in the same tanks. Activated carbon is added directly to the leaching vessels. As soon as gold dissolves, it meets carbon and is removed from solution. This continuous removal keeps the concentration of dissolved gold in the liquid phase low, which can drive the leaching reaction forward. CIL is therefore often favoured where the ore leaches slowly or where natural carbonaceous matter competes for the dissolved gold.

In a CIL circuit you carry carbon through every leach tank, so the carbon handling load is higher than in CIP. Screens must hold the loaded carbon inside each tank while slurry moves to the next. Air lifts or pumps transfer carbon countercurrent to the slurry. The advantage is that the process does not wait for the full leach residence time before adsorption begins. That can shorten the total circuit or improve recovery on ores that need the solution concentration kept low.

For a closer look at the equipment in this arrangement, you can review Xinhai's gold CIL plant solutions.

The cil vs cip decision begins in the laboratory, not on the site

You cannot pick CIL or CIP from grade and throughput alone. The decision depends on leaching kinetics, and those are measured in the laboratory before a single tank is sized. A standard test programme for a cil vs cip study runs in three numbered steps:

• Step 1: grind a representative sample to a defined P80, often 75 µm, and run cyanide bottle rolls to measure gold dissolution over 24 hours.
• Step 2: repeat the leach with activated carbon present in the same vessel or in a downstream stage, and measure adsorption rate and carbon loading.
• Step 3: compare the gold left in solution after 24 and 48 hours with and without carbon. If the carbon-in-contact test recovers more total gold, CIL is usually favoured.

P80 of 75 µm means 80% of the particles pass a 75 micrometre screen. This is a standard target for many gold milling operations, though your ore may need finer grinding. The test also shows whether preg-robbing carbonaceous matter is an issue. If the ore itself adsorbs gold cyanide complexes, keeping activated carbon in the leach tank can compete successfully for the gold, which is another reason designers lean toward CIL.

For more on the test work that underpins these decisions, see how to test gold ore.

Equipment variables that shape both routes

Once the route is chosen, tank sizing and agitation design follow from the same variables: slurry flow rate, leach residence time, pulp density, particle size, carbon concentration and the required dissolution profile. The equipment notes that inform this page list flow type (CIP/CIL/cementation), slurry throughput, gold grade, leaching time, carbon concentration, elution batch size, safety and cyanide management as the main selection variables. Those inputs determine tank volume, impeller type and power density.

For CIL and CIP circuits, Xinhai supplies dual-impeller leaching and agitation tanks up to 20 m × 20 m. The dual-impeller design helps keep fine solids in suspension and distributes cyanide and oxygen throughout the tank. Carbon handling, screening and regeneration circuits sit alongside the tanks. Screening is critical because you need to keep loaded carbon from moving with the slurry, while still letting liquid and fine solids pass.

Agitation equipment is not one-size-fits-all. Tank volume, residence time, slurry density, viscosity and impeller form all influence the selection. On a high-throughput plant you may use several large tanks in series. On a smaller or modular plant you may use fewer tanks with longer residence time. The engineering decision follows the test work, not the other way around.

Downstream recovery: elution, electrowinning and smelting

CIL and CIP share the same downstream flowsheet. Once activated carbon is loaded with gold, it is screened and sent to elution. Elution strips the gold from the carbon using a hot caustic cyanide or acid solution, producing a concentrated gold-bearing solution. Electrowinning then plates the gold onto cathodes. The final step is smelting, which produces doré bars. Because the downstream steps are common, a cil vs cip decision does not change your elution building design very much. It changes how much carbon you move per tonne of ore and how many screens and pumps you need upstream.

Xinhai's CIL/CIP scope includes elution systems sized to the circuit's carbon movement rate, electrowinning cells and gold room design. Batch size is selected to match the carbon movement rate, which is higher in a CIL circuit than in a CIP circuit treating the same ore. A larger carbon inventory requires more frequent stripping or a larger elution column.

For more detail on how the whole gold recovery chain is assembled, see gold recovery methods.

Engineering the plant around your ore

Xinhai reports that it has served more than 2,500 mines and delivered over 600 mine EPC+M+O projects in more than 100 countries. Those are company-published figures, and they describe a group with 700+ technical experts and three manufacturing bases covering approximately 110,000 m². The group produces more than 1,000 equipment types and supports flowsheets up to 50,000 t/d. For gold specifically, Xinhai's process range includes gravity, flotation, CIP/CIL cyanidation and heap leaching.

Design standards include JORC and NI 43-101 compliant documentation and VALMIN-aligned work. The design institute holds a Class B metallurgical qualification in China. Chinese qualifications are not presented as valid in other jurisdictions, so you should treat local permitting requirements separately. The CNAS-accredited laboratory runs around 5,000 element analyses per month and about 200 metallurgical tests per year, including Bond work index testing and leaching-adsorption comparisons.

If you are still in the study phase, a smaller or modular plant can be used to generate the same data. The design questions do not change with scale; the tank diameters and carbon transfer rates do. You can read about modular and small-scale layouts in modular gold processing plant or check throughput-specific case pages such as a 1,000 t/d gold plant.

Cyanide handling and the safety boundary

Both CIL and CIP use sodium cyanide or potassium cyanide as the lixiviant. Cyanide is toxic, and its handling is governed by compliance and safety procedure, not by a catalogue selection. The International Cyanide Management Code is a voluntary industry programme for gold and silver mining operations covering the production, transport, storage and use of cyanide. Signatory operations are certified through third-party audits. If your project will handle cyanide, you should plan for these controls from the start, not after the tanks are sized.

Gold cyanidation also operates within a wider mining context. Worldwide gold mine production in 2024 was an estimated 3,300 tons, according to the USGS Mineral Commodity Summaries 2025. China was a major gold producer in 2025 and accounted for around 10 per cent of total global production, according to the World Gold Council. Those figures are background, but they help explain why efficient leaching routes such as CIL and CIP remain central to the industry.

Choosing between CIL and CIP: a practical summary

If your ore leaches fast, CIP often wins. If it leaches slowly, or if preg-robbing is a concern, CIL usually wins. That is the core distinction after test work. But the final choice also includes carbon handling cost, screen maintenance, tank count and future ore variability. You might run a CIL circuit on a blended feed that includes both fast and slow components, while a consistently fast oxide ore is a stronger CIP candidate. There is no universal answer until the bottle rolls and carbon tests are done.

You do not have to make that call alone. Xinhai designs and supplies complete CIL/CIP plants, including dual-impeller leaching and agitation tanks up to 20 m × 20 m, carbon handling, screening and regeneration circuits, elution systems sized to the circuit's carbon movement rate, and electrowinning cells and gold room design. Send your ore characteristics for a route recommendation based on test work. You can reach the team via the contact page.