Carbon in Column Gold Recovery: CIC Design, Carbon Selection and Troubleshooting

By the YELI Carbon Technical Team · Published 27 October 2026 · 12 min read

What is carbon in column gold recovery?

Carbon in column is a gold adsorption process in which a gold-bearing solution is passed through granular activated carbon held in one or more columns. It is used where the feed can be clarified before adsorption, such as some heap-leach solutions, filtered leach liquors or other low-solids process streams. As solution moves through the carbon bed, the gold cyanide complex is adsorbed onto the pore surface. The loaded carbon is later removed or retained for elution, while the barren solution moves on. CIC is a contactor arrangement, not a guarantee of performance: the bed, flow rate, solution chemistry, carbon size, fines content and maintenance routines determine gold loading and hydraulic stability. The operating target is stable flow at a measurable loading rate, not simply a high initial adsorption result. This avoids selecting a carbon on one laboratory index.

The important distinction is physical. In carbon-in-pulp (CIP) and carbon-in-leach (CIL), carbon particles move through agitated tanks containing ore pulp. In CIC, the carbon normally remains in a packed or engineered column while a comparatively clear solution flows through it. That makes CIC attractive where mixing carbon through pulp is impractical, but it also moves the main operating risk from tank screening toward bed hydraulics, pressure drop and solution cleanliness.

CIC vs CIP vs CIL: where column adsorption fits

CIC, CIP and CIL all use activated carbon to capture dissolved gold, but they place the carbon in different environments. CIC keeps carbon in a column and treats a clarified solution. CIP adsorbs gold from pulp after leaching, while CIL combines leaching and carbon adsorption in the same tanks. CIC can be a practical choice for a clear, low-solids leachate, a heap-leach or filtration route, a satellite recovery unit or a plant expansion where a column circuit fits the available space. CIP and CIL remain common where the project must handle large pulp flows and already has interstage screens, agitated tanks and carbon transfer systems. The correct choice comes from a mass balance, solids separation test, solution chemistry, pilot work and site layout, not from the name of the process alone. A pre-project test should confirm that solids can be removed consistently before column performance is guaranteed.

For a broader comparison of carbon-in-leach, carbon-in-pulp and column routes, see the existing CIC vs CIP vs CIL guide. It complements this article by focusing on how the circuits differ across the full flowsheet.

Which activated carbon should a CIC plant evaluate?

A CIC plant should evaluate activated carbon as a hydraulic and metallurgical material, not as a single iodine number. Coconut shell granular activated carbon is widely used for gold recovery because its hard structure and microporous surface suit the gold cyanide complex. For each candidate, ask for the particle-size distribution, apparent or bulk density, ball-pan hardness, abrasion resistance, moisture, ash, iodine number and any gold adsorption rate or capacity test available. A 6×12 mesh cut may suit a column where that particle size retains properly and the pressure-drop budget allows it; a finer or coarser cut may be appropriate in another design. Final selection should follow a representative column test using the plant's solution, temperature and flow, because two carbons with the same iodine value can behave differently in a packed bed. The quotation should also separate the product specification from sample, packing and delivery terms.

YELI's gold-grade coconut shell GAC is offered in 6×12 mesh and 8×16 mesh, with 3×6 mm also available. The published product range is iodine 1000–1300 mg/g and ball-pan hardness ≥98%, with a batch COA. Those figures are a starting specification, not a substitute for testing the delivered lot or proving the carbon against your actual solution.

How does mesh size affect pressure drop?

Finer carbon creates more particles and smaller flow channels per unit of bed volume, so pressure drop can rise at the same superficial velocity. A wide particle-size distribution can make the effect worse because small particles migrate into the voids between larger granules. The practical result is uneven flow, local compaction and a pressure curve that may climb faster than expected. Mesh size alone does not predict the result: bed voidage, particle shape, fines, feed solids, bed depth, flow rate, temperature and the condition of the support and distribution system all matter. A supplier should provide a representative size distribution, including undersize and oversize limits, rather than only a nominal mesh label. During commissioning, record pressure differential at several flow rates and after backwashing so a baseline exists before fouling develops. If the curve is unstable, a pressure-drop guarantee based only on clean-water testing is not enough.

Use the gold carbon mesh size guide to compare 6×12, 6×16, 8×16 and 3×6 mm cuts, then check the packed-bed voidage guide for the hydraulic calculation behind the discussion.

How should a CIC column calculate bed voidage?

Bed voidage is the fraction of the packed-bed volume that is not occupied by carbon particles. A practical estimate is ε = 1 − (bulk density ÷ particle density), provided both densities are measured from the same conditioned sample and the measurement basis is stated. Bulk density is the mass of carbon divided by the settled bed volume. Particle density excludes the spaces between particles but includes the internal pores according to the stated method. If particle density is unavailable, voidage should be measured or supplied as part of the design data instead of guessed from a typical number. Voidage affects residence time, pressure drop and the volume available for fines or scale. Request the method and sample condition behind each density value, because a value measured on a dry sample cannot be compared directly with one measured on an as-packed sample.

Do not design a column from nominal density alone. Confirm the density test method, the packing procedure, the moisture basis and the expected size distribution. The YELI specification sheet records apparent density and the associated test basis for the gold-grade product.

What causes common carbon-in-column problems?

Most CIC problems appear first as a change in flow or loading, not as an obvious equipment failure. A rising pressure differential can indicate fines migration, scale, bed compaction or gas accumulation. Uneven gold loading can indicate channeling, poor solution distribution, short-circuiting or a bed that was not properly wetted. Low loading may come from unfavourable solution chemistry, too little contact time or a carbon that has lost accessible pore volume. Carbon leaving with the treated solution points to a screen, support or flow-control problem. Visible fines after transport or backwashing may indicate inadequate hardness, handling damage or an unsuitable size distribution. Record pressure drop, flow, bed level, feed clarity and loading profile together. That record makes it easier to separate a hydraulic issue from a chemical or metallurgical one. Compare the finding with the column design basis before changing the carbon grade.

For column operation, verify the direction of flow and the intended bed condition before changing carbon. Some systems are designed for a packed bed, while others use a controlled expanded or moving condition. Backwashing may help remove fines or gas, but excessive backwash can classify the bed or carry carbon out. The column design basis should state acceptable flow ranges, bed expansion limits and the action to take when the pressure trend moves outside the approved window.

How do loading, stripping and regeneration connect in CIC?

Carbon in column is only one part of the gold recovery loop. The loading stage must produce carbon that can be stripped economically, and the stripping method must suit the column and the carbon it contains. The loaded carbon may be transferred to a separate elution circuit or stripped in place, depending on the design. The eluate then goes to electrowinning or another recovery step, while the stripped carbon is washed, regenerated or returned according to the validated procedure. Column carbon should therefore be evaluated against the entire route: loading kinetics, elution performance, acid-wash or scale-control requirements, regeneration temperature, handling losses and the number of cycles expected before replacement. A carbon that loads well but breaks down during transfer can create a downstream gold-loss problem that the loading test alone will not reveal. The test should reflect the actual handling route and the intended elution and regeneration conditions. Record the method, sample basis and release criterion for every reported property.

Review the gold carbon elution guide and the regeneration cycle guide before setting a purchase specification. Ask the supplier to state whether the COA is from the exact lot and whether a retained sample can be re-tested after delivery.

How do you verify a batch COA for gold recovery carbon?

A useful batch COA connects the sample to the shipment and states the test method, result and acceptance limit for each property. For gold recovery carbon, start with mesh distribution, iodine number, ball-pan hardness or abrasion resistance, apparent density, moisture and ash. If gold adsorption rate or capacity is reported, require the method, solution conditions and the reporting basis. Check that the lot number on the COA matches the bag, pallet and shipping documents. Ask who performed the test, whether the result is a single batch or a composite, and whether the supplier can provide a retained sample. ASTM D4607 and ASTM D3802 are relevant reference methods for iodine number and ball-pan hardness; the specification sheet should state which method is used for every other value.

Read the test method before comparing numbers from two suppliers. A result without a method, sample basis or acceptance limit is difficult to verify and easy to misinterpret. The sample gold carbon COA and COA verification guide show the type of information a buyer can request before approving a shipment. Retain the sample under controlled conditions so a later dispute can be resolved with evidence.

What data should a gold plant send before requesting a CIC carbon quotation?

A useful CIC quotation request should identify the service and the hydraulic limits. Include the circuit type, feed source, expected solution flow in m³/h, operating hours, feed gold grade, pH, temperature, cyanide concentration and suspended solids. For the column, provide diameter, bed depth, number of columns, design pressure drop, backwash or flow direction, and the screen or support details. State whether carbon will be stripped in place or transferred, and give the elution, acid-wash and regeneration conditions. Add the required mesh cut, iodine band, hardness limit, moisture and ash limits, packing, delivery port and target trial quantity. If the plant has a previous COA or an operating problem, include it. These details let a supplier quote a compatible specification rather than a generic bag price. A complete request lets the supplier identify a hydraulic or materials limit before a price is quoted.

Use this checklist to compare quotations consistently. It also reduces the risk that a low price is hiding a wider size distribution, lower hardness, unclear test method or unsuitable packing.

1. Circuit route and whether the feed is truly clarified.
2. Flow, gold tenor, temperature, pH, cyanide and suspended solids.
3. Column diameter, bed depth, pressure-drop limit and backwash design.
4. Required mesh distribution and acceptable fines.
5. Iodine, hardness, density, moisture and ash limits.
6. Stripping and regeneration conditions.
7. Batch COA, retained sample and third-party test options.
8. Packing, port, trial quantity and delivery schedule.

Send your CIC operating data Download the specification checklist

What should a CIC carbon pilot test measure?

Use a representative sample of the same solution the plant will treat, or a synthetic solution matched to its chemistry when approved by the metallurgical team. Run the candidate carbons under the intended flow and temperature, with the same bed depth and preconditioning where practical. Record pressure drop at several flow rates before loading begins. Sample the outlet at planned intervals to build breakthrough curves, and measure loaded-carbon gold to see the profile through the bed. After loading, evaluate elution and regeneration under the proposed conditions. A pilot that reports only a single adsorption number misses the two questions that matter to CIC: can solution pass through the bed at a stable hydraulic cost, and can the loaded carbon be stripped and reused without losing its useful structure?

Keep the raw data. Flow, temperature, solution assays, pressure differential, mass of carbon, mesh analysis and any deviations from the plan are more useful than a paragraph of conclusions. If a supplier provides a technical recommendation, ask which operating assumptions were used and which values remain to be confirmed on site. Keep the raw data and test conditions so a later comparison can be audited.

Carbon-in-column FAQ

Is carbon in column the same as carbon in pulp?

No. CIC normally treats a clarified solution in a column. CIP treats ore pulp in agitated tanks and uses screens to keep carbon in the adsorption stage. Both use activated carbon, but their feed preparation, equipment and operating risks differ.

Is 6×12 or 8×16 mesh better for CIC?

Neither size is universally better. A coarser cut can reduce pressure drop and improve retention on a support, while a finer cut can change kinetics and bed behaviour. Decide with the column design, flow, solution cleanliness and pilot pressure-drop data.

Does higher iodine value always mean better gold recovery?

No. Iodine number is an indicator of pore development, not a complete gold-recovery specification. Compare iodine with mesh distribution, hardness, density, fines, adsorption data and the carbon's performance in the actual solution.

What is the first sign of a fouled CIC bed?

A rising pressure differential at a controlled flow is a common early signal. Confirm whether the cause is suspended solids, fines, scale, gas or compaction before changing the carbon grade. Record the pressure trend after backwashing as part of the diagnosis.

Technical references and evidence