INFRARED AND X-RAY PHOTOELECTRON-SPECTROSCOPY STUDIES ON THE ADSORPTION OF GOLD CYANIDE ON ACTIVATED CARBON

The understanding of the adsorption of gold cyanide on activated carbo n has greatly benefited from recent investigations using Mossbauer X-r ay photoelectron (XPS) and infrared (IR) spectroscopy. While Mossbauer spectroscopy produced definitive results, XPS and IR spectroscopy hav e not achieved the same irrefutable success. XPS binding energies diff ered from one study to another because of uncertainties in calibration . IR studies, on the other hand, are difficult because of the opacity of activated carbon. In addition, no systematic analysis of IR results has been offered XPS and IR spectroscopy were, therefore, performed o n KAu(CN)(2) and Au(CN)(2)- adsorbed on activated carbon. XPS results in the literature, after corrections, and from this study agree remark ably well with each other The IR data were analysed in terms of the Ho oke's law approximation of absorption frequencies and a molecular orbi tal model of the cyanide radical. In combination, the XPS and IR resul ts are consistent with the adsorption of gold cyanide by a weak donati on of pi-electrons from activated carbon to gold. The adsorbed species is most likely the unpaired dicyano complex, which does not undergo a ny chemical change other than the adsorption interaction itself No evi dence was found to support the ion-pair adsorption model. To the contr ary, the model becomes self contradicting when scrutinised with the IR and XPS results.