Abstract
The effect of Acidithiobacillus ferrooxidans on the humic-acid passivation layer on pyrite surfaces was studied by atomic-force microscopy, leaching experiments, and adsorption experiments. Atomic-force-microscopy results showed that humic-acid was adsorbed onto the pyrite surface. The bacteria grew and reproduced on the humic-acid layer. Leaching experiments showed that the humic-acid passivation layer prevented the oxidation of pyrite by Fe3+ under aseptic conditions. Bacteria destroyed the humic-acid layer, promoted pyrite oxidation, and increased the oxidation of pyrite from 1.64% to 67.9%. Bacterial adsorption experiments showed that the humic-acid passivation layer decreased the speed of bacterial adsorption on the pyrite surface but had no effect on the number of bacteria adsorbed on the pyrite surface. The maximum number of bacteria adsorbed by pyrite with and without the humic-acid layer was 4.17 × 1010 cells∙mL−1 and 4.4 × 1010 cells∙mL−1, respectively. Extracellular polymeric stratum layer of bacteria cultured at different concentrations of humic-acid was extracted and analyzed. This layer could destroy the humic-acid layer and promote pyrite oxidation.
Highlights
With the depletion of treated gold resources, the exploitation and utilization of refractory gold resources of the Carlin-type has attracted the attention of countries globally
Our results showed that humic-acid stimulated the secretion of extracellular polymeric stratum (EPS) by bacteria, and the EPS layer could adsorb the humic-acid
Atomic-Force Microscopy (AFM) showed thathumic-acid the humic-acid adsorbed on pyrite the pyrite surface formed a passivation
Summary
With the depletion of treated gold resources, the exploitation and utilization of refractory gold resources of the Carlin-type has attracted the attention of countries globally. Humic-acid is a large-molecule organic substance that contains groups such as carboxyl, phenol, hydroxyl, quinine, and ketone. It has a high physiological activity, and exhibits good absorption, complexation, and exchange properties [6,7]. Previous studies have shown that humic-acid is readily adsorbed on pyrite surfaces, and forms an effective passivation layer, which prevents pyrite oxidation [13,14,15]. No research exists on the effect of bacteria on the humic-acid passivation layer, which is important in the application of bacterial oxidation in Carlin-type gold deposits. The morphology of the humic-acid layer on the pyrite surface after adsorption of.
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