For many small and medium-sized CIP/CIL gold plants in Africa, low recovery is not always caused by leaching problems or outdated equipment. In quite a few cases, the real issue is the activated carbon itself.

This was exactly the situation faced by a small gold mine in West Africa. The plant had stable ore grades and a relatively standard CIL process, yet gold recovery remained inconsistent for a long time. Operators also noticed excessive carbon loss and rising reagent consumption month after month.

After several rounds of troubleshooting, the mine eventually identified the activated carbon as one of the main causes affecting recovery performance.

Plant Background

The mine processes approximately 300 tons of oxidized gold ore per day using a conventional CIL circuit. Ore characteristics are relatively stable, with low sulfide content and fine-grained gold distribution.

Before the upgrade, the plant had been purchasing low-cost industrial activated carbon from a local supplier. The initial goal was simply to reduce procurement costs, but operational problems gradually became more obvious during continuous production.

Plant operators reported several recurring issues:

• Carbon particles breaking down quickly inside adsorption tanks

• Large amounts of carbon fines appearing around interstage screens

• Higher residual gold levels in tailings

• Recovery fluctuations between different production cycles

At first, the plant suspected cyanide concentration and pH instability. Several parameter adjustments were tested, including increased cyanide dosage and stronger agitation intensity, but the improvement remained limited.

Problems Found During Site Inspection

After reviewing operating records and checking the adsorption circuit on site, several carbon-related problems became clear.

The original activated carbon had relatively low hardness and poor wear resistance. Under long-term slurry agitation, the carbon generated excessive fines, and some gold-loaded fine carbon escaped through the screen system together with tailings.

In addition, the carbon showed weak adsorption activity after repeated cycles. Micropore distribution was uneven, which reduced its ability to capture dissolved gold complexes efficiently.

Operators also observed that the carbon became contaminated rather quickly, especially when ore clay content increased during rainy periods.

Carbon Upgrade Solution

The mine decided to replace the original material with a dedicated coconut shell activated carbon designed specifically for gold recovery applications.

No major process changes were made during the trial period. The plant kept the same:

• pulp pH range

• cyanide concentration

• stirring speed

• desorption conditions

• regeneration process

This allowed the mine to evaluate the carbon performance more accurately without interference from other variables.

Results After 30 Days of Operation

The improvement did not happen overnight, but after continuous operation for about one month, the production data became noticeably more stable.

Compared with the previous operating period:

• Overall gold recovery increased from 78% to around 90%

• Tailings residual gold dropped from 0.42 g/t to 0.18 g/t

• Carbon attrition decreased significantly

• Carbon replacement frequency was reduced

• Adsorption performance remained more stable between cycles

One noticeable change reported by plant operators was the reduction of fine carbon accumulation near the screen area. This helped reduce hidden gold loss that had previously gone unnoticed during routine operation.

The plant also found that the new carbon maintained adsorption efficiency better after regeneration, which extended usable service life compared with the previous material.

Economic Impact

Although the upgraded activated carbon had a higher purchase price, the mine found that overall operating costs became easier to control.

Lower carbon loss reduced replacement demand, while improved recovery generated additional gold output without modifying the existing production line.

For a relatively small processing plant, this type of optimization required minimal investment compared with large-scale equipment upgrades.

According to internal production estimates, the recovery improvement alone created a noticeable increase in monthly gold output.

Final Feedback from the Plant

After several months of continued operation, the mine maintained recovery rates above 90% with fewer fluctuations than before.

Plant managers concluded that the previous recovery issues were not mainly caused by leaching chemistry or equipment limitations, but by the mismatch between ordinary industrial carbon and actual gold recovery requirements.

For CIP/CIL operations, activated carbon quality directly affects adsorption stability, carbon loss, regeneration efficiency, and ultimately the overall economics of the plant.

In many cases, upgrading carbon performance can be one of the simplest ways to improve recovery without major process reconstruction.