Spectral study of humic substance extract from pressurized oxidizing slag of Carlin-typed gold deposit

Carbonaceous matters in Carlin-type gold deposit, especially the humic substance, which have a serious preg-robbing effect on the process of cyanidation. In this paper, the humic acid and fulvic acid were extracted from oxidizing slag via pre-activation alkaline-heat method, and using FTIR and UV-Vis spectra to study the molecular structure of humic acid extract and fulvic acid extract. The FITR spectrum demonstrated that hydroxyl, carboxyl and benzene rings characteristic stretching vibration peaks occurred in spectra of humic acid and fulvic acid, but humic acid extract had a finer molecular structure. The result of UV-Vis spectra analysis showed that the extract contained alkyl-substituted benzene ring structure, and the amount of carboxyl groups and hydroxyl groups in fulvic acid molecule was larger than that of humic acid. The fulvic acid extract contained more chromophores, while humic acid molecules have a higher degree of humification and a higher average molecular weight. Although there were some differences in the molecular structure of the both, they were both complex macromolecular organic compounds with a benzene ring as a basic unit.