Two Consumables That Decide Recovery
Every leach plant in Tanzania, from a vat leach site in Chunya to a CIL plant in Geita, depends on two imported consumables: sodium cyanide to dissolve the gold and activated carbon to capture it. Neither is made locally. When either runs short or arrives off-specification, recovery falls and gold goes to the tailings. Tanzanian miners have been through cyanide shortages before, and the operations that kept running were the ones that had planned stock and supply.
Activated Carbon
What to specify
- Raw material: coconut shell. Coconut shell carbon is harder than coal-based carbon and breaks down less in agitated tanks. For CIL, CIP and elution it is the standard choice
- Particle size. 6x12 mesh (about 1.7 to 3.4 mm) is common; 8x16 is used in some circuits. The size must suit your interstage screen aperture or carbon will pass through
- Hardness, commonly specified at 98 percent or above. Soft carbon turns to fines, and fines carry gold straight to the tailings
- Activity, often quoted as iodine number or gold loading capacity. Higher activity loads gold faster
- Moisture and ash content, which affect how much carbon you actually get per bag
What it costs and where it comes from
Gold-grade coconut shell carbon is imported mainly from India, Sri Lanka, the Philippines, Indonesia and China. International suppliers publicly quote bulk carbon from around USD 1,800 per tonne FOB for Tanzanian gold customers, before freight, duty and inland transport. Shipments from India typically reach Dar es Salaam faster than from China. Prices move with the coconut shell market, so confirm current quotes before budgeting.
Making carbon last
- Condition new carbon by washing out fines before it goes into the tanks
- Regenerate it in a kiln after elution. Carbon that is never regenerated loads less gold each cycle
- Screen and recover fines from tailings where the grade justifies it
- Check interstage screens every week, because worn screens lose carbon into the tailings
Sodium Cyanide
What to specify
- Form. Solid briquettes are the normal form for small and medium plants. They are shipped dry and dissolved on site
- Purity, usually 98 percent or above
- Packaging. Sealed drums or bags inside boxes, rated for hazardous goods transport, with clear labelling
- Documentation: safety data sheet, certificate of analysis, and the paperwork your import and transport permits require
Buying legally in Tanzania
Sodium cyanide is an industrial chemical controlled in Tanzania. Importing, storing, transporting and using it needs the appropriate registration and permits through the Government Chemist Laboratory Authority and the environmental and mining authorities, and your plant must hold its own approvals to use it. Buy only from registered suppliers who can provide the chain of documentation. Cheap cyanide without paperwork puts the whole operation at risk of closure, and unknown purity makes dosing unreliable.
Requirements change, so confirm current rules with the regulator or a registered chemical agent before you import or buy.
Storage and handling
- Dry, locked, ventilated store, away from acids. Cyanide in contact with acid releases lethal HCN gas
- Stock register recording every container in and out
- Raise pH first. Slurry or solution should be at pH 10.5 or above with lime before cyanide is added
- HCN detectors, ventilation, emergency shower and eyewash at the mixing point
- Trained staff and a written emergency plan, including first aid for cyanide exposure
Research among small-scale miners in northern Tanzania found that most workers were not aware of the International Cyanide Management Code. Training is the cheapest safety measure a plant can buy.
Lime and Other Reagents
- Hydrated or quick lime for pH control. Tanzanian lime is available, but quality varies, so check its available calcium content
- Caustic soda for elution eluant
- Hydrochloric acid for carbon acid washing
- Flocculant where a thickener is used
- Smelting fluxes: borax, silica and sodium nitrate
Planning Supply So the Plant Never Stops
- Hold stock for the full re-order lead time plus a margin. For imported cyanide and carbon, that often means two to three months of consumption
- Consolidate orders into full containers to cut freight per tonne
- Qualify two suppliers for each critical reagent, so one shortage does not stop production
- Test each delivery for carbon hardness and cyanide strength before it goes into the circuit
- Model consumption per tonne from your own plant records, not from supplier estimates
Regions We Serve
Frequently Asked Questions
Which activated carbon is best for gold?
Coconut shell carbon at 6x12 or 8x16 mesh, with high hardness. It resists breakage in agitated tanks and during elution, which keeps gold-bearing fines out of the tailings.
How much activated carbon does a plant need?
The initial fill depends on tank volume and the carbon concentration the circuit runs, commonly 10 to 25 grams per litre of pulp. On top of that, plan for ongoing make-up to replace carbon lost to breakage. Your plant designer should give you both figures.
Can I reuse activated carbon?
Yes. Carbon is stripped in elution, regenerated in a kiln and returned to the circuit many times. It is replaced only as it breaks down or loses activity.
Why is my cyanide consumption so high?
The usual causes are copper minerals or sulphides in the ore, pH that is too low, too much cyanide added at the start, or old tailings that contain reactive material. A diagnostic leach test identifies which one applies.