Study On Adsorption Of The Moderately Thermophiles Onto The Pyrite Surface

Pyrite is the most common sulfide mineral and could offer the elements of iron and sulfur, which is important for the mineral bioleaching. In this work, the moderately thermophiles Acidithiobacillus caldus, Sulfobacillus thermosulfidooxidans and Leptospirillium ferriphilum were used to study the microbe-mineral interactions and surface properties of both the bacteria and pyrite at the different culturing conditions.Firstly, under the different culturing temperatures (40℃and 45℃) and pH values (1.6,2.0 and 2.5), the bacterial adsorption rates of the pure cultures and the mixed culture (S. thermosulfidooxidans:L. ferriphilum A. caldus=1:1:1) onto the pyrite were different. At 40℃, L. ferriphilum exhibited the highest adsorption rate of 89.47% at pH 2.0; A. caldus and mixed culture with an adsorption rate of 83.33% and 75.54% respectively at pH 1.6. According to the analysis of bacterial contact angles and Zeta potentials, pyrite cultured bacteria had bigger contact angles and isoelectric point (IEP) than those of bacterial cultivated in ferrous ion or sulphur solution, which indicated that pyrite cultured bacteria had stronger hydrophobic property and bacterial surface functional groups changed. However, a similar change trend of pyrite cultured bacterial surface properties was found.Secondly, the change of pyrite surface after interaction with the bacteria was studied by Scanning electron microscopy (SEM), Energy dispersive X-ray microanalysis (EDAX) and X-ray photo-electron spectrum (XPS). In solution with bacteria, both the reduced trend of pH values and the rising trend of oxidation-reduction potential were much more obvious than those in sterile solution. In addition, according to the results of SEM, EDAX and XPS analysis, many bacteria adsorbed onto the pyrite surface, and the pyrite surface was not smooth and corroded severely after interaction with microorganisms.The electrochemical behavior of pyrite was studied. In absence and presence of bacteria, pyrite was firstly oxidized to S at the potential of 0 V (vs. SCE), which covered the pyrite electrode and made electrode passivate. With the scanning potential increasing, the polarizing current increased rapidly and S was oxidized to SO42-, which made the passive film dissolved. Decreasing pH values accelerated the oxidation rate of the pyrite. In presence of bacteria, both corrosion potential and corrosion current of pyrite was higher than those in sterile solution, which showed that bacteria promoted the oxidation of pyrite...