Gold recovery is one of the most demanding applications for activated carbon. The carbon must load the gold–cyanide complex quickly, survive months of mixing with abrasive ore slurry, and keep doing both through repeated reactivation. Coconut-shell carbon has become the standard for the job, but not all coconut carbon is equal. This guide explains the specifications that actually decide performance and cost.
Why Coconut Shell
Gold recovery needs a microporous carbon with high iodine value and outstanding hardness. Coconut-shell carbon delivers both: its naturally dense structure resists the abrasion of slurry mixing, and its narrow micropore distribution adsorbs the gold–cyanide complex efficiently. Coal and wood carbon are used in some circuits, but coconut dominates where hardness and reactivation economics matter most.
The Three Specifications That Matter
Three numbers decide the choice. Iodine value reflects the total micropore volume available for gold loading; 1000 mg/g and above is standard for CIP duty, with 1050+ preferred for fast loading. Hardness, measured by the abrasion test, predicts how much carbon is lost to fines during mixing and transfer — a one-point difference can mean thousands of dollars over a plant's life. Mesh size keeps the moving bed stable and prevents screen blinding; 6×12 and 8×16 are the common choices, matched to your screen aperture.
How to Evaluate Carbon Before You Commit
The right way to compare suppliers is with a side-by-side trial, not a datasheet. Use a consistent mesh and test method, allow enough contact time for a fair comparison, and measure both loading rate and abrasion loss. If two carbons load gold at the same rate but one loses noticeably less to fines, the harder carbon is almost always the better long-term buy — because replacement cost is the largest operating cost in the circuit.
Also ask for the batch test data with every shipment, not just a one-off certificate. Consistent iodine value and hardness from batch to batch is what lets the plant run without retuning, and that consistency shows up in the documentation a supplier provides.
If you are building a new plant, run the carbon trial at your actual process conditions — the slurry density, contact time and temperature you will operate at — rather than a bench test with clean water. Loading rate and abrasion loss both shift with these conditions, and a carbon selected at bench scale can underperform in the real circuit. For an existing plant, compare the new carbon against your current one in the same tank train over at least one full reactivation cycle, and track carbon make-up rate rather than the purchase price. That number, more than any spec, tells you which carbon is cheaper to own.
FAQ
Which mesh do CIP plants use?
Most CIP/CIL plants run 6×12 or 8×16 coconut carbon; 3.35/1.18 mm is used where the screen aperture requires it.
What iodine value do gold plants need?
1050 mg/g and above is standard, balancing fast loading with acceptable reactivation economics.
Why does hardness matter so much?
Hard carbon survives more reactivation cycles and produces fewer fines, which directly lowers replacement and carbon-loss costs.
Send us your plant details for a carbon specification and free sample tailored to your circuit.
