By the YELI Technical Team · Updated September 2026 · 8 min read
Short answer: CIC (carbon-in-column), CIP (carbon-in-pulp) and CIL (carbon-in-leach) all use the same family of coconut-shell granular carbon, but the duty differs. In a CIC column the carbon must survive continuous fluid scouring without shedding fines: order 6×12 or 8×16 mesh coconut GAC, iodine 1000–1300 mg/g, hardness ≥98% (ASTM D3802) and platelet content <1.5%, with a COA on every batch. VAT-CIC plants — common for smaller West African mines and old-tailings retreatment — treat clear pregnant solution, so the carbon never sees pulp, but it sees flow.
Gold circuits are usually described by how the carbon meets the ore. That one decision changes what the carbon has to survive — and therefore which specification protects your recovery and your operating cost.
1. CIC, CIP and CIL: what each circuit actually does
CIP (carbon-in-pulp) is the classic route: ore is leached in cyanide as a slurry, and carbon is added to the pulp tanks, moving counter-current and screened between tanks. CIL (carbon-in-leach) merges leaching and adsorption into the same tank train, which suits ores that preg-rob. CIC (carbon-in-column) is different: no pulp contact at all. The ore is leached first — in a vat, a heap, or a pond — to produce a clarified gold-bearing solution, and that solution is pumped through columns packed with granular carbon. VAT-CIC is the small-mine workhorse: simpler equipment, no interstage screens, and a carbon bed that is easier to elute and regenerate.
Data anchors to compare like for like
- Hardness ≥98% — ASTM D3802 ball-pan (GB/T 12496.6)
- Platelet content <1.5% — de-flaked, water-polished granules
- Iodine 1000–1300 mg/g — GB/T 12496.8 / ASTM D4607
- Mesh 6×12 / 8×16 / 3×6 mm — GB/T 12496.2 / ASTM D2862
- Moisture ≤5% · Ash ≤5% — as packed
- K-value 8–12 kg Au/t · R-value 52–58% (2 h) — GB/T 32992—2016, in-house QC, per batch
2. Carbon spec matrix: VAT-CIC vs CIP vs CIL
| Duty factor | VAT-CIC (column) | CIP / CIL (slurry) |
|---|---|---|
| Carbon contact | Fixed/expanded bed in column; clear pregnant solution flows through | Carbon suspended in ore pulp in stirred tanks |
| Main wear source | Fluid scouring at design flow; eductors/pumps during carbon transfer | Interstage screens, pumps, elution, kiln — mechanical abuse |
| Hardness (ASTM D3802) | ≥98% — fines carry gold out of the bed | ≥98% — attrition fines escape screens |
| Platelet content | <1.5% — flakes channel the bed and raise pressure drop | <1.5% — flakes blind interstage screens |
| Typical mesh | 6×12 or 8×16 mesh (1.70–3.35 / 1.18–2.36 mm) | 6×12 or 3×6 mm, matched to interstage screens |
| Iodine value | 1000–1300 mg/g — fast loading in solution | 1000–1300 mg/g — consistent lot to lot |
| Moisture / ash | ≤5% / ≤5% as packed | ≤5% / ≤5% as packed |
| Gold adsorption data | K-value 8–12 kg Au/t & R-value 52–58% (2 h) per GB/T 32992—2016 | Side-by-side bottle-roll on your own pulp recommended |
3. Why hardness ≥98% and platelet content <1.5% protect your gold in a CIC column
In a vat-leach CIC plant the carbon bed can sit in the column for weeks. What abrades it is not mechanical screening but fluid scouring: solution moving through the bed at design flow, plus the eductors and pumps used when you transfer carbon to the elution column. Every point of hardness you give away becomes fines — and fines that pass the nozzle screens carry adsorbed gold with them out of the circuit, into the elution tail or the tailings pond.
Platelet content is the specification most buyers skip. Flakes are flat particles that look fine on a sieve but behave badly in a bed: they orient across the flow, create channels where solution shortcuts past the carbon, raise pressure drop, and break faster under scouring. A de-flaked, water-polished granule stays round, packs evenly, and keeps the whole bed working. That is why we hold platelet content below 1.5% and state it on request alongside hardness.
4. Reading the spec: what a real COA should show
For CIC duty, the COA that matters covers five numbers on the actual lot: iodine value (GB/T 12496.8 / ASTM D4607), hardness (GB/T 12496.6 / ASTM D3802), moisture (≤5%), ash (≤5%) and the full sieve analysis for the cut your columns were built around. Fines and platelet content should be stated, with the method. K-value (gold loading capacity, mg Au/g) and R-value (adsorption rate) describe adsorption dynamics and are tested in our own QC laboratory per GB/T 32992—2016, with the result reported on the batch COA. Standard of production and testing: YS/T 3038—2020 (Granular Activated Carbon for Gold Production).
5. Start with a sample pack, not a container
Before you commit volume, order a 3-grade sample pack (iodine 1000 / 1100 / 1200) with the COA of each exact lot, and run a small column or bottle-roll test on your own pregnant solution. If your circuit is a vat-leach CIC plant, test at your real flow and contact time — that is the number that decides loading and barren losses, and it cannot be read off a brochure.
Need Gold-Grade Carbon for a CIC Column or CIP/CIL Plant?
We produce coconut shell GAC for gold recovery at our own factory in Longyan, Fujian — 6×12/8×16 mesh, iodine 1000–1300, hardness ≥98%, platelet content <1.5%, COA with every batch. Tell us your circuit (VAT-CIC, CIP or CIL), solution flow and target iodine, and we will confirm a grade within 24 hours.
See Gold Carbon Specs →FAQ: Frequently Asked Questions
CIC (carbon-in-column) treats clear pregnant solution: the gold-bearing liquid flows through fixed beds of granular carbon, typically after vat or heap leaching. CIP (carbon-in-pulp) and CIL (carbon-in-leach) contact the carbon directly with the ore pulp in stirred tanks — CIL does leaching and adsorption in the same tank, CIP in separate tanks with counter-current carbon transfer. CIC is common on smaller vat-leach plants, on old tailings re-treatment, and wherever the mine already produces a clear solution.
In a column the carbon is not stirred, but it is still scoured: pregnant solution flows through the bed at design flow, carbon is transferred by eductors or pumps for elution and regeneration, and every cycle abrades the particles. Soft carbon sheds fines, and fines are the main route by which adsorbed gold physically leaves the circuit. Coconut-shell gold carbon with hardness ≥98% (ASTM D3802 ball-pan method) keeps attrition low and protects both the column screens and your gold balance.
Platelets are flat, flaky particles that survive screening but pack badly in a column. In our production the carbon is water-polished (de-flaked), and platelet content is held below 1.5%. Flakes create channeling (solution shortcuts through the bed), raise pressure drop, and break into fines faster under flow. For CIC duty, low platelet content matters as much as hardness.
Most CIC columns run 6×12 mesh (1.70–3.35 mm) or 8×16 mesh; some designs use 3×6 mm for larger columns. Match the cut to your column internals — nozzle screens, distributor slots and the elution column — because changing mesh later is a redesign. Ask for the full sieve analysis with each batch, not just a nominal mesh size.
K-value (gold loading capacity) is 8–12 kg Au/t (≈ 8–12 mg Au/g) in high-grade circuits, and R-value (2-hour adsorption rate) is 52–58% of equilibrium loading within 2 h in a standard ~1000 ppm Au cyanide solution. Both are measured in our own QC laboratory per GB/T 32992—2016 and the result is reported on the batch COA. For routine lot control, iodine value, hardness and platelet content on the COA catch most quality drift; run a K/R test or a side-by-side bottle-roll on your own solution when you qualify a new supplier or grade.
A well-operated carbon train typically recovers 95–99.5% of the dissolved gold per contact series, leaving 0.01–0.02 mg/L Au in the barren solution; overall plant recovery from ore to bullion usually lands in the 90–97% band. Carbon is one link in that chain — hardness, platelet content and consistent iodine from batch to batch all feed the number.