| Description |
The effect of particle size on gold adsorption and elution from activated carbon has been studied in alkaline solution, in order to understand the nature of gold losses on fine activated carbons, to improve the rate of gold recovery, and to develop an innovative way of treating preg-robbing gold ores. Four stripping techniques (atmospheric Zadra, syringe and press, syringe pump, and filter press elution methods) have been used to evaluate the effect of particle size, temperature, pressure, and strip solution composition on the desorption of gold cyanide from activated carbons. The atmospheric Zadra elution method was studied as a batch process using continuous (without solution replacement) and incremental solution replacement methods at atmospheric pressure and elevated temperatures. However, in the other three stripping methods, pressure was employed to force strip solutions through a bed of carbon placed in a syringe or filter press. In general the rates of adsorption and elution were found to increase with a decrease in particle size as expected. However, in the case of atmospheric Zadra stripping there were some anomalous results which seem to be related to the experimental procedure used. Pregrobbing ore was received, prepared, and leached using fine magnetic activated carbon (MAC) after which the MAC particles were separated by a wet high gradient magnetic separator. In this way almost 70% of the gold was recovered in less than 6 hours compared to previous CIL results, which indicated that about 55% of the gold could be recovered in 24 hours using granular activated carbon. In summary, it has been substantiated from this research that particle size, temperature, pressure and composition of the strip solution used in the elution process are factors that are interdependent in the influence they have on the elution of gold cyanide from activated carbons. These factors must all be set at their proper levels in order to maximize the rate and amount of gold desorbed from the loaded carbons. Finally, it has been shown that fine activated carbon particles can be loaded and stripped with ease and have some potential for the treatment of preg-robbing gold ores. |
