Preparation and properties of ferrite derived from iron oxidizing bacteria

Abstract

The growth characteristics of Sphaerotilus natans and Leptothrix discophora SS-1 (ATCC43182) were first used to fabricate the ferrite and manganese ferrite. The scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and vibrant sample magnetometer (VSM) were used to make clear their morphology microstructure, chemical composition, crystal structure, and magnetostatic characteristic. The result showed that the hollow ferrite fibers were prepared successfully, whose crystal structures were close to α-Fe 2 O 3 and the average aspect ratio was over 50. Moreover, the soft magnetic manganese ferrite was fabricated with the saturation magnetization Ms at 25 emu/g and coercive force H c at 796 A/m. Biological manufacturing is an emerging cross-disciplinary, which could achieve the efficient and environmentally friendly fabrication of micro/nano functional materials or devices [1,2]. Bio-growth forming is a new method to obtain the required functional materials or products with the direct use of the microbial growth characteristics [1]. For example, the microbe is used to pharmaceutical fermentation, or the magnetotactic bacteria is used to synthesize single domain Fe 3 O 4 [3,4]. Currently, in the areas of materials, the study of magnetic materials represented by ferrite has become a hotspot, and it is widely used in the manufacture of new high-tech products, like electromagnetic absorbing materials, magnetic recording materials, magnetic fluids, catalytic materials, coating or paint [5,6]. It was shown that iron bacteria are widespread in various types of nature waters, which have the capacity of oxidizing and depositing ferrous ions and manganese ions in water efficiently. This microbe could be directly used to obtain composites with a variety of shapes such as fiber, tube and film [7][8][9][10][11][12][13][14][15][16] and has the potential to fabricate the ferrite materials. Compared to traditional chemical synthesis [5], there may be a breakthrough in the aspects of physical control, particle reunion and industrialization.In this paper, according to the enrichment and deposition mechanism of iron and manganese [7][8][9][10][11][12], the sediment composition, the microstructure characteristics [15] and other basic research of iron bacteria, the Sphaerotilus natans which were separated from activity mud of Xiamen sewage treatment plant and the Leptothrix discophora which was purchased from ATCC, were used to deposit the iron and manganese ions respectively. The Sediments were collected and heat treated at high temperature to obtain the ferrite. And then the product morphology and static magnetic properties were characterized.

Uranium(VI) Scavenging by Amorphous Iron Phosphate Encrusting Sphaerotilus natans Filaments

“…related strain BoFeN1 in laboratory biomineralization experiments conducted in a phosphate rich medium. , Secondary oxidation of Fe­(II) by nitrite produced by enzymatic nitrate reduction explains the formation of amorphous Fe­(III)–Fe­(II) phosphate within the periplasm and its growth on the BoFeN1 cells, as well as at distance from the cells, as shown for the biomineralization of ferric oxyhydroxides by the same strain in phosphate poor medium. , In contrast, S. natans has not been recognized to actively oxidize iron although a recent study by Park et al (2014) suggests that this bacterium could couple nitrate reduction with iron oxidation. Nevertheless, various iron oxyhydroxides including ferrihydrite have been shown to be deposited on S. natans sheaths in laboratory experiments, the nature of which depends on the culture conditions . More generally, iron biosorption by S. natans has also been reported for samples from water treatment systems and water streams. − In the present study we demonstrated that amorphous iron phosphate can be deposited on S. natans sheaths, upon oxidation of dissolved Fe­(II) in a phosphate rich medium, either in a bacterial suspension or via sorption on a supported biofilm.…”

“…Nevertheless, various iron oxyhydroxides including ferrihydrite have been shown to be deposited on S. natans sheaths in laboratory experiments, the nature of which depends on the culture conditions . More generally, iron biosorption by S. natans has also been reported for samples from water treatment systems and water streams. − In the present study we demonstrated that amorphous iron phosphate can be deposited on S. natans sheaths, upon oxidation of dissolved Fe­(II) in a phosphate rich medium, either in a bacterial suspension or via sorption on a supported biofilm. In addition, as detailed in the next section, we show that this amorphous mineral phase has a strong ability to bind uranyl species that are known to be among the most mobile uranium species under oxidizing conditions.…”

“…64,65 In contrast, S. natans has not been recognized to actively oxidize iron 29 although a recent study by Park et al (2014) 39 suggests that this bacterium could couple nitrate reduction with iron oxidation. Nevertheless, various iron oxyhydroxides including ferrihydrite 66 have been shown to be deposited on S. natans sheaths in laboratory experiments, the nature of which depends on the culture conditions. 67 also been reported for samples from water treatment systems and water streams.…”

Optical and electrical properties of porous silicon impregnated with Congo Red dye

“…By illumination, azo dye can generate isomerization reaction between trans and cis, which is reversible and results in the change of the absorption coefficient. [23][24][25][26] This work reports the preparation and the preliminary characterizations of a hybrid material formed by the combination of PS with Congo Red (CR), an acidic pH indicator. The optical properties of CR/PS system are characterized by Fourier transformer infrared (FTIR) and photoluminescence (PL) spectroscopy methods.…”