Ultrasonic elution of gold from activated carbon

The feasibility of using ultrasound to enhance the elution of gold from activated carbon was investigated. A laboratory-scale elution column immersed in an ultrasonic bath was used to investigate three eluant systems. The kinetic activity of the activated carbon was improved in the elution with sonication. Ultrasonic radiation improved the recoveries and kinetics of elution considerably. This could possibly be attributed to an increase in diffusive transport caused by acoustic vortex microstreaming and microjets, as well as the prevention of activated carbon fouling which can lead to the blockage of active sites. The rate of elution was significantly increased by the addition of ethanol to the aqueous eluant, especially in the presence of ultrasound. It could be attributed to the increased activity of smaller ions in preference to gold cyanide in the presence of ethanol. Ethanol, by capturing the primary radicals (H^* and OH^*), generated secondary radicals (C₂H₄OH*) which could be responsible for the increased efficiency. The introduction of ultrasound into the conventional elution systems made it possible to elute gold cyanide from activated carbon under less severe conditions.