The mechanism of interaction between ore fines and porous adsorbents
Activated carbon and ion exchange resins are being used extensively in the mining industry to extract metal cyanides from leached liquors. Recently, ion exchange membranes and fibres have been investigated as possible alternatives to carbon and resin. This paper describes the interaction between fine ore particles and porous adsorbents in a batch reactor. Gold cyanide was used as an adsorbate to detect changes in the mass transfer characteristics of the adsorbents. These changes were evaluated using a film/surface diffusion model, with specific emphasis on the diffusion and equilibrium parameters. Tests involving the intrusion of ore particles into the adsorbents indicated that the adsorption profile for gold cyanide is affected only for activated carbon and ion exchange resins. These results were confirmed by ashing tests, scanning electron microscopy and secondary ion mass spectrometry performed on the adsorbents. However, the diffusion of gold cyanide to all adsorbents was inhibited owing to the physical blinding of the superficial surface by the fine particles in suspension. This result was obtained by exposing a presaturated adsorbent to the suspended ore particles and dissolved gold cyanide. The effect of blinding was accounted for in the model with the introduction of an availability factor.