Experimental study of the influence of sulfur on gold sorption by bitumen at 200–400°C and 1 kbar Pressure

Abstract

The effect of sulfur on the sorption of gold by carbonaceous matter (CM) was investigated under hydrothermal conditions (200–400°C and 1 kbar) using the autoclave-ampoule method. The model CM was represented by asphaltenes fractionated from the lignite of the Pavlovskoe coal field. The source of gold was the walls of the Au container, which were dissolved in water under the experimental conditions. Sulfur was added as finely ground pyrite (C-S-Fe-O-H-Au system) or elemental sulfur powder (C-S-O-H-Au system). The contents of Au were measured by atomic absorption spectrometry with electrothermal atomization in quenched aqueous solutions (WF), soluble organic fraction (SF), and insoluble residue (kerogen). The lowest Au concentration was detected in the WF, −8.96 < logmAu < −6.32. The Au concentration is higher in the SF (−5.02 < logmAu < −4.34) and increases by more then an order of magnitude in the kerogen, −3.94 < logmAu < −2.33. The IR spectra of the experimental products showed that sulfur was accumulated in the kerogen, whereas no C-S functional groups were observed in the SF. This is the reason for the negligible influence of sulfur in this system on Au concentration in the SF. The maximum Au concentration was detected in the kerogen in the presence of pyrite, which was transformed into pyrrhotite at 400°C. Thus, iron sulfides promote Au uptake by kerogen from ore-bearing hydrothermal fluids.