Adsorption of Gold with
Activated Carbon

Tests, using a solution containing 20 mg/l of gold, were taken into use to determine the adsorptive capacity of the activated carbon. With the intention of disposing the most data and which at the same time results trustworthy, new carbons and used carbon previously reactivated have been used.

One can observe the existence of similar characteristics of adsorption. When referring to the behavior of the reactivated carbon, it is worth taking note its good efficiency, presenting a slight advantage when the process of reactivation is effectuated at 700°C. As a consequence, the carbon will be able to be used every time, after a stage of reactivation.

Desorption and Electrodeposition
The desorption of gold was effecuated using sollutions of NaCN-NaOH-alcohol, for which it was proceeded to evaluate and determine the optimal levels of these reactives. The three types of carbon gave high recuperations of gold for three stages of desorption:

• Carbon A: 91.26% Recuperation
• Carbon B: 89.80% Recuperation
• Carbon D: (reactive 700°C) 90.67% Recuperation

The sollution of desorption was circulated through the cells of electrodeposition Zadra type. The high efficiencies obtained in this stage (98%) have been seen favored by the use of wool of steel as a cathode which due to its major superficial area allows a good deposition of gold. In the same manner, the presence of NaOH in the electrolyte facilitates the conductivity of the sollution.

Scaling Parameters
Once the optimal parameters are determined, we proceeded to perform a scaling for the initial treatment of 1,000 tons of mineral.

Base: 1,000 tons

*Lixiviation

• Specific gravity: 2.5 TM/m3
• Volume = 1,000/2.5 = 400 m3
• Height of the mineral: 2 m.
• Area = volume/Height = 400/2 = 200 m2
• Length: 20 m.
• Width: 10 m.

For effects of security it is considered a factor of 30% in the base, Afterwards:

• Length: 26 m.
• Width: 13 m.
• Specific flux: 10 l/h/m2
• Lixiviant flux: 10 l/h/m2 x 200 m2 = 2,000 l/h = 8.8 gal/min.

* Adsorption

• Height of the column: 2 m. (5 columns disposed in series)
• Diameter of the column: 30 cm.
• Load in each column: 80 Kg.
• Size of the particle of carbon: 6 x 16.
• System of the fluidized bed.