Investigation of biogenic iron-containing nanoscale composite materials

Biogenic composites are interesting as green and sustainable precursors for preparation of advanced materials of various applications. Biomaterials from Leptothrix group bacteria cultivated in two feeding media of silicon-iron-glucose-peptone (SIGP) and Lieske were studied. Iron-containing biogenic powders and biofilms on silica gel covered aluminum plates were prepared. They were studied to elucidate the effect of the plates in the process of growing biogenic iron nanotubes. The cultivation period was varied from 4 to 30 days. Biomass phase composition and physicochemical properties were studied by Mössbauer spectroscopy at room and low temperature, as well as by means of powder XRD, FTIRS, and SEM methods. Mössbauer analysis offered us a unique possibility to register iron oxide species at the different steps of biogenic material formation. Tetrahedrally coordinated iron species were registered at an early stage of biofilm formation. So, important results on the mechanism of biomineralization process are obtained. The reaction of CO oxidation on prepared biomaterials was studied using in situ DRIFTS. Comparative analysis of the obtained materials and examination of spent samples showed differences in their phase composition, stability and dispersity. Changes of the phase composition were observed during catalytic tests with biomasses obtained in Lieske feeding media. No differences in biogenic powder and biofilm composition and dispersity were registered when SIGP media was used neither for studied bacteria cultivation period nor in spent catalysts. These results indicated the stabilizing effect of extra silicon content in the feeding media. Formation of iron oxihydroxide nanotubes was also established in this case.