Common Gold Elution Problems and How to Fix Them

When Your Elution Circuit Stops Performing

Every elution plant operator has experienced the sinking feeling of checking recovery numbers and finding they have dropped. Gold that should be on your cathodes is either stuck on the carbon, lost in the tailings, or somewhere in between. The good news is that most elution problems have identifiable causes and fixable solutions.

Drawing on years of experience with Zimbabwe gold processing operations, here are the most common problems I see — and exactly how to fix them. If you need a refresher on how the process should work, read my gold elution process guide first.

Problem 1: Incomplete Gold Stripping from Carbon

Symptoms

Barren carbon still has high residual gold loading. You are eluting for the expected time but not getting the gold off the carbon.

Common Causes and Fixes

• Temperature too low: The most common cause. For Zadra, the eluant must reach 95–100°C. For AARL, the top-of-column temperature should be 110°C. Check your thermocouples — they drift over time and give false readings. Replace annually.
• Insufficient caustic/cyanide concentration: The NaOH and NaCN in your eluant drive the desorption reaction. If concentrations are too low, gold stays on the carbon. Test your reagent makeup solution before each cycle.
• Flow rate too high: Pushing eluant through the column too fast reduces contact time. Slow down — a complete Zadra cycle should take 10–14 hours, not 6.
• Carbon poisoning: If the above checks are all normal and stripping is still poor, your carbon may be poisoned or severely fouled. Try a fresh batch of carbon — if it strips normally, your existing carbon needs replacement.

Problem 2: Low Gold Recovery at Electrowinning

Symptoms

The eluate is gold-rich (confirmed by assay) but gold is not depositing effectively on the cathodes. Your smelted product is lower than expected.

Common Causes and Fixes

• Incorrect cell voltage: Electrowinning cells should operate at 2.5–3.5 volts. Too low, and gold does not plate. Too high, and you waste power and can damage cathodes.
• Exhausted steel wool cathodes: Steel wool dissolves over time as iron goes into solution. Replace cathodes when they have visibly thinned or when recovery drops despite normal eluate grade.
• Short-circuiting in the cell: Gold buildup or displaced steel wool can create direct contact between anode and cathode, bypassing the electrowinning reaction. Inspect cells regularly.
• Eluate temperature too high: If the eluate enters the electrowinning cell above 60–70°C, gold deposition efficiency drops. Allow cooling or install a heat exchanger.

Problem 3: Gold Losses to Tailings

Symptoms

Your adsorption circuit is not capturing all the dissolved gold. Tailings assays show unacceptably high gold values.

Common Causes and Fixes

• Insufficient carbon in the adsorption circuit: If your CIP or CIL circuit does not have enough active carbon relative to the gold in solution, dissolved gold passes through uncaptured. Increase carbon concentration.
• Carbon activity too low: Fouled or poisoned carbon adsorbs gold slowly. Test carbon activity and replace or regenerate as needed.
• Carbon screening failure: Broken or worn screens allow fine carbon to pass into the tailings — taking adsorbed gold with it. Inspect screens regularly.
• Excessive carbon fines: High attrition generates fines that pass through screens. Review your carbon handling procedures to reduce mechanical damage.

Problem 4: Elution Taking Longer Than Expected

Symptoms

Your cycle time has gradually increased from 10–12 hours to 16–20 hours to achieve the same stripping result.

Common Causes and Fixes

• Carbon degradation: As carbon degrades, its internal pore structure changes and gold is held more tightly. This is cumulative — eventually the carbon needs replacing.
• Scale buildup in the column: Calcium and silica scale can restrict flow and reduce heat transfer. Descale your column with acid periodically.
• Boiler inefficiency: An ageing boiler may not maintain adequate temperature, slowing the reaction. Service and calibrate heating equipment regularly.
• Channelling: If eluant flows preferentially through channels in the carbon bed rather than evenly through the entire bed, some carbon is never properly contacted. Ensure even carbon packing and proper bed support.

Problem 5: Safety Incidents

Elution plants handle hot caustic solutions, hydrochloric acid and cyanide. Safety is not optional.

• Ensure all operators have adequate PPE — face shields, acid-resistant gloves, protective clothing
• Maintain emergency showers and eyewash stations within 30 seconds of all chemical handling areas
• Never work alone in the plant — always have a buddy
• Keep cyanide antidote kits (amyl nitrite, sodium nitrite, sodium thiosulphate) on site and train all operators in their use
• Ensure adequate ventilation, especially around the elution column and acid wash area

The Power of Good Record Keeping

The single most effective troubleshooting tool is detailed, consistent records. Log every cycle: carbon weight, estimated gold loading, stripping efficiency, reagent concentrations, temperatures at start and end, eluate grade, electrowinning recovery and any anomalies. When something goes wrong, your records will tell you exactly when the deviation started and what changed.

Struggling with a persistent elution problem? Contact Craig Riley for practical troubleshooting advice. I work with gold elution operations across Zimbabwe and can often diagnose issues remotely from your operational data before needing a site visit.

Frequently Asked Questions

How often should I have my elution circuit audited?

At minimum, annually. If you are experiencing unexplained recovery drops, bring in expert help immediately — each day of poor recovery is lost revenue.

Can I fix most problems without buying new equipment?

Yes. The majority of elution problems are operational — wrong temperatures, incorrect reagent concentrations, poor carbon management or inadequate maintenance. These are fixable with knowledge, not capital.

What recovery rate should I be targeting?

A well-run Zadra elution should achieve 93–97% gold stripping from carbon. AARL plants should achieve 97–99%. If you are consistently below these ranges, something needs investigation.

Is it worth upgrading from Zadra to AARL?

Only if your operation has grown to the point where the faster AARL cycle time (more batches per day) and higher efficiency justify the capital investment. For most small-scale Zimbabwe operations, a well-optimised Zadra plant is perfectly adequate.