Effects of the textural and surface properties of activated carbon on the adsorption of gold Di-Cy anide

摘要

The influence of the surface condition of activatedcarbon on the adsorption of aurodicyanide was investigated to gaina better understanding on the influence of the pore volumedistribution and heat treatment on the adsorption capacity of thecarbon Three activated carbons were heat-treated at 850 deg C innitrogen gas. Adsorption of gold di-cyanide on heat-treated carbonincreased compared to the untreated carbon. However, no drasticchange in the pore volume was observed after heat treatment of theactivated carbon. Therefore, the combined effects of textural andsurface properties of the activated carbon are relevant for theequilibrium adsorption of gold di-cyanide.In the second part of the paper one of the major assumptions inadsorption modelling onto activated carbon based on aqueoussurface chemistry principles is investigated; that of accounting forelectrostatic interactions. The surface of activated carbon containsacidic and basic surface groups, which influence the adsorption ofgold di-cyanide from the aqueous solution. The surface chargedensity that arises from ionisation of these surface groups inresponse to the solution pH and ionic strength was evaluated bypotentiometric titration. The surface potential based on the Gouy-Chapman relationship for a flat surface does not reflect a realisticpicture of the potential distribution inside the microporous carbonas the size of the micropore is too small to allow such a potentialdistribution to develop. This currently forms the basis availableadsorption models. It is proposed that the overlapping of thepotential fields inside the micropores could be handled by usingthe Donnan potential.