Fixation of potassium aurocyanide on active carbons Original Research Article

Active carbons of different origins (ex-coconut shell, ex-coal, ex-peat and ex-wood) have been used as adsorbents of potassium aurocyanide. Various treatments were applied to the active carbons: heat treatment at 800 °C, heat treatment at 800 °C followed by HCl (11) washing, heat treatment at 650 °C, washing with HCl 10%, esterification with methanol, oxidation with nitric acid and extraction with toluene. The oxygenated surface groups contents were determined. Further, the kinetics of adsorption of KAu(CN)2, from 10 and 100 ppm buffered aqueous solutions, were established. The amount of fixed gold was measured by UV spectrometry. The gold cyanide uptake is related to the basic surface groups content of the non-modified carbons. An increase in basic surface groups content following an adequate treatment is accompanied by a noticeable increase of the gold derivative uptake capacity. Differences in adsorption kinetics and capacities are noticed, the improvement being related to better accessibility and definitively to a larger amount of basic groups.