Coconut Shell Charcoal for Gold Extraction in Africa

By the YELI Technical Team - Updated November 1, 2026 - 12 min read

Short answer: Select gold-recovery coconut shell carbon by circuit fit, not by iodine value alone. Confirm whether the plant uses CIL, CIP or heap-leach CIC; match mesh to screens, columns and transfer equipment; assess slurry abrasion and solution chemistry; compare adsorption rate and loading capacity; then verify batch consistency and lifecycle cost with a fixed test method.

Why coconut shell charcoal suits African gold plants

Coconut shell charcoal for gold extraction in Africa is processed into hard granular activated carbon for CIP/CIL or CIC circuits; raw charcoal itself is not the final adsorption medium. For African gold plants, the practical selection starts with circuit type, screen aperture, slurry chemistry, throughput and destination port, then sets mesh, iodine band, hardness, density, moisture and ash limits against named test methods. A 6×12 mesh coconut shell GAC is a common starting point for CIP/CIL, but the plant must verify it against its own screens, elution column and fines balance. Require an exact-lot COA and a representative sample before scaling. Delivery terms should identify FOB or CIF scope, packing, quantity, lead time and the port, such as Tema, Abidjan, Dakar, Lagos, Mombasa or Dar es Salaam. These details make competing supplier quotations comparable and testable.

Activated carbon captures gold from cyanide leach solution as the Au(CN)₂^- complex. The loaded carbon is later stripped, the gold is recovered from the strip solution, and the carbon is regenerated and returned to the circuit. A good gold-grade carbon must perform across that whole loop, not only in a beaker test.

This guide separates what iodine, CTC, hardness, mesh, density, ash and moisture actually measure from what they do not. It also shows how to select a practical starting specification for CIL, CIP and heap-leach carbon-in-column systems, and which plant data should be exchanged before a supplier quotes.

1. What activated carbon does in a gold plant, and what it cannot do

In a cyanide circuit, gold dissolves as Au(CN)₂^-. Activated carbon adsorbs the complex onto its internal pore surface. The carbon must then release the gold in the elution circuit, survive thermal regeneration, and return to adsorption without excessive breakage.

That is a chain of linked operations. Carbon performance depends on:

• pore structure and adsorption kinetics;
• gold concentration and contact time;
• competing copper, iron, thiocyanate and organic species;
• slurry viscosity, clay, lime scale and abrasive solids;
• carbon concentration, advance rate and interstage screens;
• elution, acid-wash and regeneration capacity.

A carbon specification can control the properties of the carbon. It cannot by itself guarantee a plant recovery or a fixed loaded-carbon assay. Those outcomes must be measured across the full circuit.

2. Read gold-carbon specifications correctly

K/R is not tested in YELI's in-house QC laboratory. If required, the buyer may appoint an independent laboratory to test a representative sample under GB/T 32992-2016. K/R results are not part of the standard batch COA.

Iodine value is not a gold-loading number

Iodine number is usually reported in mg/g and is widely used as an indicator of micropore volume. For gold-grade coconut shell carbon, practical inquiry ranges often sit around 1000-1300 mg/g, depending on the supplier and the plant's objective. A higher number may point to more developed porosity, but it does not tell you how many kilograms of gold will be on each tonne of carbon in a CIL tank.

The field result is controlled by solution grade, carbon concentration, carbon advance rate, residence time, competing ions and whether the carbon approaches equilibrium. If the circuit is limited by screening losses, elution capacity or regeneration, increasing iodine may add cost without moving recovery.

Make the number contract-ready by stating the method, basis and tolerance. ASTM D4607 and GB/T 12496.8 are commonly referenced iodine tests, but two reports are not comparable if the test method, sample preparation or moisture basis differs. See our iodine-value test guide and COA verification checklist for the details.

CTC is useful, but it is not a selectivity test

Carbon tetrachloride activity, usually called CTC, is a defined pore-capacity test. Gold-carbon enquiries often ask for CTC of at least 55%, with higher values requested for some complex projects. That can be a reasonable secondary specification, but CTC does not measure whether carbon prefers gold over copper.

Copper cyanide complexes can enter the same carbon and create downstream load. A high-CTC carbon does not reject them. High-copper operations need solution-chemistry control, suitable cyanide and oxygen management, adequate carbon movement, elution design and, where appropriate, pretreatment such as SART. Carbon selection supports that work; it does not replace it.

If CTC is important to your purchasing team, fix the method and the minimum value in writing. ASTM D3467 is one recognized carbon tetrachloride activity method. Do not compare a CTC result from one laboratory method or sample basis with another as if the numbers were interchangeable.

Hardness and platelet content protect the carbon inventory

In CIL, carbon stays in contact with abrasive slurry while it is mixed, screened, transferred, stripped and regenerated. Weak granules become fines. Those fines can blind screens, leave with tailings and carry adsorbed gold out of the circuit.

For demanding CIL service, specify high ball-pan hardness with a named method, such as ASTM D3802 or GB/T 12496.6. Also look at platelet or flake content, shipping breakage and hardness after regeneration. A hardness certificate from a fresh, carefully selected sample is only part of the story.

Our current gold-grade product specification targets hardness of at least 98% by GB/T 12496.6 / ASTM D3802, with platelet content below 1.5%. Buyers should still verify the result on their incoming lot and compare like-for-like test reports. Read the full explanation in why carbon hardness matters in gold recovery.

Mesh must match the plant before it matches an industry habit

6×12 mesh, approximately 1.70-3.35 mm, is a common cut for CIP and CIL. It offers a practical balance of surface area, diffusion path, screen retention and hydraulic behavior. It is not a universal answer.

8×16 mesh can approach equilibrium faster because the diffusion path is shorter, but smaller granules may pass undersized screens, raise pressure drop in a column, or increase fines losses. A 3×6 cut may suit particular column duties. The right decision begins with interstage screen apertures, elution-column dimensions, kiln feed limits and carbon-transfer equipment. Use the gold-carbon mesh guide before changing the cut.

Density, ash and moisture affect cost and operation

Apparent density changes how many kilograms of carbon a tank or container holds at the same volume. Two quotes at the same price per tonne are not equivalent if one carbon arrives at 450 kg/m³ and the other at 520 kg/m³. Compare delivered mass, tank charge and freight as well as the headline price.

Ash can reduce the useful carbon fraction and may indicate mineral residue or soluble impurities. Low ash is generally desirable, but the required limit should match the feed chemistry. Acid washing can remove some soluble species; it is not a substitute for diagnosing scale, silica, oil or organic fouling.

Moisture affects shipping weight and the basis of a COA. It does not mean that water has permanently filled the pores and made the carbon useless. Carbon is wetted in a slurry by design. Protect packed carbon from rain and condensation, agree the moisture limit, and compare iodine, hardness and ash on the basis stated in the certificate.

3. Match the grade to the circuit

Leach chemistry remains the first control

Carbon cannot correct an unstable leach. Before comparing grades, confirm the target pH, free cyanide, dissolved oxygen, temperature, pulp density and mineralogy. Cyanidation is often operated around pH 10.5-11 to limit cyanide loss and acid formation, but the actual set point must come from the ore and metallurgical test work. Excessive lime can also create scale, so a higher pH is not automatically better.

Interpret head grade together with leach recovery and solution assays. Carbonaceous ore can preg-rob gold, sulfide and copper minerals can consume cyanide or load complexes onto carbon, and oil, flotation reagent, humic material or calcium can foul the carbon. These are circuit problems that may require pre-treatment, solution clarification, acid washing or a change in operating strategy, not simply a different iodine number.

CIL versus CIP: a trade-off, not a ranking

CIL can adsorb gold while leaching is still taking place and may shorten the window in which gold is exposed to competing carbonaceous material. The trade-off is that the carbon is also exposed to the leach chemistry, abrasive slurry, copper, lime scale and other fouling species. CIP separates leaching from adsorption, which can simplify the carbon duty, but it may leave more opportunity for preg-robbing before the carbon stage and needs enough residence time in the adsorption train.

The correct comparison is therefore site-specific: ore mineralogy, kinetic tests, carbon loading, elution capacity and tailings loss should be evaluated together.

For continuous CIL

Start with a mesh that the screens can retain, then prioritize high hardness, low platelet content and consistent activity. Carbon consumption is often a stronger economic signal than a 50 mg/g difference in iodine. Track make-up carbon, fines generated, loaded-carbon assay, tail-solution gold and activity after regeneration together.

If the circuit already achieves high adsorption efficiency and the main loss is screen blinding or carbon attrition, changing to a more expensive high-iodine grade is unlikely to solve the problem. Review the screen-blinding guide and carbon-consumption diagnosis first.

For CIP

CIP can place more emphasis on kinetics and loading because the adsorption stages are separate from the leach tanks, but the plant's contact time and countercurrent flow still determine the result. A carbon with a favorable R-value direction can sometimes deliver more value than a higher iodine number with slower kinetics. Test with representative liquor when the adsorption train is tight.

For heap leaching, use CIC terminology

Heap-leach projects usually pass clarified pregnant solution through carbon columns or beds. That is carbon-in-column or carbon-in-leach? It is CIC, not CIP. The distinction matters because column design, pressure drop, backwash and feed clarity drive the carbon selection.

Do not carry a CIP mesh assumption into a column without checking hydraulic loading and bed expansion. See our dedicated carbon-in-column design guide.

4. Head grade is not the same as solution concentration

A grade of 2 g/t means approximately 2 g of gold per tonne of dry ore. It is not 2 g per tonne of slurry and it is not a direct measure of the gold concentration reaching the carbon.

For an illustrative calculation, if 1 tonne of ore contains 2 g of gold and all of it dissolves into a leach volume of about 4 m³, the solution would contain roughly 0.5 g/m³, or 0.5 mg/L, before adsorption. Real plants use measured pulp density, solution volume and leach recovery; the example only shows why ore grade and solution grade must not be confused.

Higher head grade can increase the gold load, but it does not automatically justify the highest iodine grade. The selection decision depends on the solution concentration profile, carbon inventory, advance rate, required loaded-carbon assay and elution schedule. The detail is covered in iodine 1000 vs 1100 for CIL plants.

5. Feedstock origin is useful context, not a performance certificate

Indonesia, the Philippines, Sri Lanka, India and Vietnam can all supply coconut shell for activated carbon. Shell thickness, maturity, moisture, contamination and carbonization practice influence the starting material. However, origin alone does not determine hardness, pore structure or gold performance.

Activation control, screening, de-flaking, washing, laboratory testing and batch traceability can matter more than a country label. A supplier should be able to show incoming-shell control, process records, a batch COA and retained samples.

YELI's gold-grade production uses Indonesian and Philippine coconut shell, selected for dense shell and consistent activation. Buyers should still validate the actual lot rather than accept a country claim as a substitute for inspection. Compare our coconut shell and coal-based carbon comparison and factory verification guide.

6. What to send before requesting a gold-carbon quotation

A useful quotation starts with operating data. Send these eight items:

1. Circuit type: CIL, CIP, CIC or another process.
2. Daily ore throughput and solution or slurry flow.
3. Pulp density, viscosity, temperature and solids characteristics.
4. Head grade, leach-solution gold concentration and expected recovery.
5. Copper, iron, sulfur, thiocyanate, oil or organic-carbon indicators.
6. Interstage screen aperture, elution-column size and regeneration equipment.
7. Target mesh, iodine, CTC, hardness, ash and moisture limits.
8. Destination port, packaging, annual volume and required delivery date.

With only "coconut carbon, iodine 1000" to work from, a supplier can quote a generic grade but cannot demonstrate that it fits your plant.

7. A practical sample and trial protocol

1. Request a sample and the COA from the same production lot.
2. Use the mine's actual leach solution or a representative synthetic solution.
3. Compare candidate carbons at the same mesh, carbon dose, temperature and contact time.
4. Measure adsorption rate, equilibrium loading direction, attrition and fines generation.
5. Request K/R testing by an agreed laboratory, for example under GB/T 32992-2016, where the decision depends on capacity or kinetics.
6. In a plant trial, run a mass balance on carbon added, loaded carbon, tail solution and fines lost.

Do not choose a supplier from a single advertised loaded-carbon number. Loaded carbon in operating plants often falls somewhere in the range of roughly 3,000-10,000 g Au/t, but that is an industry planning reference, not a supplier guarantee. Your solution chemistry and carbon movement determine the actual value. See K-value and R-value selection for a test-led approach.

8. Purchase specification and COA checks

A gold-carbon purchase order should identify the product, test methods, guaranteed limits, sampling and acceptance route. At minimum, require:

• feedstock and manufacturing route;
• mesh range and undersize/oversize limits;
• iodine value with method, basis and tolerance;
• ball-pan hardness with method;
• platelet content if relevant to the circuit;
• apparent density;
• ash and moisture limits;
• CTC only if the buyer and supplier agree on a meaningful method and limit;
• lot number, sample date, retained sample and packing details;
• third-party testing rights.

Our standard gold-carbon specification sheet and sample COA illustrate a documented route. For clause wording, use the 6×12 mesh purchase specification guide.

9. Frequent mistakes in gold-carbon selection

• Buying iodine value alone. Capacity, kinetics, hardness, mesh and batch consistency all affect value.
• Treating CTC as selectivity. Copper cyanide complexes are not rejected by a high CTC number.
• Changing mesh without checking screens. Carbon is lost when particles pass the interstage panels or blind the bed.
• Assuming country of origin guarantees quality. Process control and lot evidence decide the result.
• Promising a fixed loaded-carbon assay. Test under representative conditions and agree a range.
• Ignoring fines. Gold on carbon fines that leave the circuit is still gold loss.
• Comparing different test methods. A method mismatch can look like a performance difference when there is none.

Frequently asked questions

This article is a technical selection guide. It does not replace site-specific metallurgical testing, plant design or third-party certification.