By the YELI Technical Team · Updated August 2026 · 6 min read
Ask any metallurgist running a carbon-in-pulp or carbon-in-leach circuit which carbon they buy, and the answer is almost always the same: coconut shell granular activated carbon. That is not tradition — it is the result of three measurable properties that directly affect gold recovery and operating cost.
Key figures that matter in gold recovery
- 95–99.5% — share of dissolved gold a well-run CIP/CIL carbon train typically recovers per contact series
- 0.01–0.02 mg/L Au — typical barren-solution gold after carbon polishing
- 3,000–10,000 g Au/t — typical gold loading on carbon before elution
- 90–97% — typical overall plant recovery, ore to bullion (carbon is one link in the chain)
1. Hardness: The Spec That Pays for Itself
Gold carbon is abused. It is screened, transferred by pumps and eductors, stripped in elution columns and roasted in regeneration kilns. Every move grinds the particles. Soft carbon breaks into fines, and fines do three bad things: they escape the screens and carry adsorbed gold with them, they blind the elution column, and they force you to buy make-up carbon more often.
Coconut shell carbon routinely tests at 95%+ hardness, while coal-based grades sit lower. Over a year of operation, a circuit processing 2,000 tonnes of ore per day might cycle 30–40 tonnes of carbon. A difference of even 2% in attrition is a difference of nearly a tonne of carbon a year — and at $2,000+ per tonne for gold-grade GAC, that is real money, before you count the gold lost in the fines.
How is that hardness actually measured? The standard method is the ball-pan test (ASTM D3802): a 100 g sample is tumbled with steel balls for a fixed time, and the fraction retained on the reference sieve is reported as a percentage. Coconut shell gold-grade carbon typically comes back at 96–99%, while many coal-based grades sit at 90–95%. In plant terms, make-up carbon commonly runs 20–100 g per tonne of ore — and soft carbon pushes you to the top of that band, every month. When a COA lists hardness, check that it states the method; a number without a method cannot be compared.
2. Pore Structure: Where the Gold Goes
Gold cyanide complexes are small molecules, so the carbon needs a well-developed micro-pore network to give them enough adsorption sites. Coconut shell carbon has a naturally fine, uniform micro-porosity that suits gold loading very well. That is why a good coconut GAC can load 8–12 kg of gold per tonne of carbon in a high-grade circuit, and why it regenerates predictably — the pores recover their capacity after each kiln cycle.
3. Iodine Value and Gold Loading: Read Them Together
Iodine number is the most quoted number on any datasheet, but it is a proxy, not the target. For gold duty, a coconut GAC with iodine 1000–1300 mg/g is the practical band. What matters more is that the iodine figure stays consistent from batch to batch, because your circuit was designed around a certain loading rate. A supplier who ships one great batch and one mediocre batch is the real risk — ask for the COA of the actual lot you are buying, not a brochure figure.
Gold loading is not a datasheet number — it is measured. The standard check is a bottle-roll test: take your ore and your plant solution, run our carbon and a reference carbon side by side at the same pulp density and contact time, then fire-assay the loaded carbon. Typical plant loadings run 3,000–10,000 g Au/t (0.3–1.0% by mass) before elution; high-grade circuits can reach 8–12 kg/t. That side-by-side number, on your ore, is the only one worth negotiating on.
Buy on consistency, not on the best number in the brochure. Your elution schedule was built around a spec, and it needs that spec every month.
4. Ash and Moisture: Small Numbers, Steady Effects
Low ash (under 5%) means less inert material weighing down your carbon charge and fewer impurities bleeding into the pregnant solution. Moisture matters mainly because you are paying freight on it — 5% moisture on a 20-tonne order is a tonne of water at sea freight rates. Confirm the moisture content is measured at loading, not when the bag was sealed.
5. Sizing: Match the Carbon to the Screen
Gold carbon is normally supplied in 6×12 mesh or 3×6 mesh. The right cut depends on your interstage screens, elution column and kiln. Changing mesh size is a plant redesign, so order the cut your circuit was built around, and ask for the full sieve analysis with each shipment.
Need Gold-Grade Carbon You Can Trust?
We produce coconut shell GAC for CIP/CIL at our own plant in Longyan, Fujian — 1000–1300 iodine, ≥98% hardness, COA with every batch. Tell us your circuit size and we will recommend a grade and delivery plan.
See Gold Carbon Specs →Case Study: 120 Tonnes of Coconut GAC for a Mombasa CIL Plant
In 2026 we supplied a 120-tonne order of 6×12 coconut shell GAC to a gold CIL plant in Mombasa, Kenya — shipped in container lots with a COA issued for every batch. We have also supplied the same grade to buyers in Ghana via Tema and across West Africa on 5–7 week schedules, alongside 25 kg and jumbo bag options to fit each plant's handling setup.
For a plant manager comparing suppliers, the real risk is not the brochure — it is whether the lot that arrives matches the lot that was tested. Every order we ship is tested by the ASTM D3802 ball-pan method, documented, and traceable to its batch COA, which states iodine value, hardness, moisture, ash and particle size. If you want that same certainty for your circuit, send us your spec and we will quote FOB or CIF within 2 working hours.
The Bottom Line
Coconut shell carbon dominates gold plants because it is genuinely better at the job — harder, better pore structure, and consistent enough to plan around. When you compare suppliers, compare the COAs of real lots, not the marketing numbers. And if you are sourcing from a factory for the first time, read our checklist for buying activated carbon from a Chinese factory before you place the order.
FAQ: Coconut Shell Carbon in Gold CIP/CIL Plants
Three measurable properties: hardness of 95%+ (less attrition, fewer gold-carrying fines), a fine micro-pore structure that loads gold cyanide complexes quickly, and batch-to-batch consistency. Coal-based carbon is cheaper per ton but wears faster and loads gold more slowly, so life-cycle cost favors coconut shell in CIP/CIL.
Gold-grade coconut shell GAC: iodine 1000–1300 mg/g, hardness ≥98%, moisture ≤5%, low ash (under 5%), in 6×12 or 3×6 mm cuts. Every batch should ship with a COA covering these parameters, and a full sieve analysis for the cut your circuit was built around.
A good coconut GAC can load 8–12 kg of gold per tonne of carbon in a high-grade circuit, depending on solution grade, contact time and carbon activity. Iodine value is a useful proxy for surface area, but what matters is consistent loading from batch to batch — ask for the COA of the actual lot.
You can load it, but most plants that try switch back. Coal carbon has a wider, more mesoporous pore structure and lower hardness, which means slower gold loading, more attrition fines carrying gold out of the circuit, and less stable regeneration. Coconut shell carbon's fine micro-pores and ≥98% hardness are why it is the standard.
In a correctly operated circuit the 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 (ore to bullion) usually lands in the 90–97% band. Carbon is one link in the chain — hardness, loading and regeneration all feed that number. Ask us for a side-by-side bottle-roll test on your ore.