FOURIER-TRANSFORM INFRARED SPECTROPHOTOMETRIC STUDY OF ADSORBED AUROCYANIDE SPECIES ON ACTIVATED CARBON

Evidence from Fourier-transform infrared spectrophotometric studies confirms that aurocyanide species adsorb onto activated carbon without undergoing chemical change. However, the results do not enable any distinction to be made between aurocyanide in the form of M(n)+[Au(CN)2-]n ion pairs and Au (CN)2- adsorbed onto ion-exchange sites. In spectra of each of the Li+, K+, Cs+ and Ca2+ salts of aurocyanide loaded onto carbon, a CN stretch band occurred at 2140 cm, which is characteristic of the Au (CN)2- ion. No bands due to AuCN (2200 to 2250 cm-1) were observed. Cs+Au(CN)2- displayed the 2140 cm-1 band, as well as a band at 2156 cm-1, due to the CsAu(CN)2 salt, which becomes the dominant species after the carbon has been dried at 120-degrees-C. The presence of crystalline CsAu(CN)2 on the dried carbon was confirmed by scanning electron microscopy.