Adsorption of gold-cyanide complex (Au(CN)2-) on nanoporous carbon and carbon spheres

In the Carbon-In-Pulp process, Au(CN)2- is adsorbed onto nanoporous carbon (activated carbon) directly from the cyanide ore pulp, followed by the elution of adsorbed gold from activated carbon1. A comparative investigation for the adsorption of the gold-cyanide complex (Au(CN)2-) on nanoporous carbon and carbon spheres was conducted to assess their potential for the aforementioned hydrometallurgical application. The nanoporous carbon used was commercial-based, cylindrically-shaped (size > 1.4 mm), extruded activated carbon manufactured by steam activation process while micro-sized carbon spheres (diameters 0.5 to 1 μm) were hydrothermally synthesised using a glucose precursor2,3 in a pressurised digestion vessel. Kinetic-based adsorption (i.e. bottle roll kinetic testing) studies were performed with both adsorbents characterised by scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) and surface analysis. Results indicated that adsorption using nanoporous carbon was kinetically more favorable than carbon spheres, which was most probably attributed to the high surface area of the former.