Surface characterisation of pyrite exposed to A. brierleyi

The surface of pyrite exposed to the thermophilic archaeon Acidianus brierleyi was investigated to elucidate the impact of extracellular polymeric substances (EPS) and/or cells on mineral surface hydrophobicity. The interaction of cells with the surface of pyrite and the physicochemical properties of the mineral surface were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), captive bubble contact angle measurements and time of flight – secondary ion mass spectrometry (ToF-SIMS). The ToF-SIMS results show no clear evidence of EPS on the pyrite surface after exposure to A. brierleyi and further suggests significant contamination of the surface by the yeast extract included in the recommended A. brierleyi growth medium. It was found that the presence of yeast extract made it impossible to accurately determine the action of EPS on the surface, and potentially impeded chemical and biological reactions and interactions on the surface. Investigation of the impact of A. brierleyi on pyrite in the absence of yeast extract found up to 24° decrease in contact angle compared to the control after 2 h. It was found that A. brierleyi produced very little EPS and as such is unlikely to alter the surface through a contact mechanism, with little to no cell attachment observed on the pyrite surface. Thus removal of yeast extract may improve the application of this archaea to biomining applications.