Iron Oxalate Humboldtine Crystallization by Fungus Aspergillus niger

Microfungi were able to alternate solid substrate in various environments and play a noticeable role in the formation of insoluble calcium oxalate crystals in subaerial biofilms on rock surfaces. The present work describes how iron oxalate dihydrate humboldtine is acquired under the influence of the acid-producing microscopic fungus Aspergillus niger on the surface of two iron- bearing mineral substrates in vitro. Pyrrhotite and siderite rocks, as well as the products of their alteration, were investigated using a complex of analytical methods, including powder X-ray diffraction, optical microscopy, scanning electron microscopy and EDX spectroscopy. The effect of the underlying rocks with different composition and solubility and different oxidation states of iron on Fe-oxalate crystallization and on the morphology of humboldtine crystals was shown. The mechanisms of humboldtine formation were discussed. The results obtained in vitro seem promising for using fungi in bioleaching iron and other metals from processed ores and for the development of environmentally friendly biotechnologies.

Mesoporous Iron(III)-Doped Hydroxyapatite Nanopowders Obtained via Iron Oxalate

Mesoporous hydroxyapatite (HA) and iron(III)-doped HA (Fe-HA) are attractive materials for biomedical, catalytic, and environmental applications. In the present study, the nanopowders of HA and Fe-HA with a specific surface area up to 194.5 m2/g were synthesized by a simple precipitation route using iron oxalate as a source of Fe3+ cations. The influence of Fe3+ amount on the phase composition, powders morphology, Brunauer–Emmett–Teller (BET) specific surface area (S), and pore size distribution were investigated, as well as electron paramagnetic resonance and Mössbauer spectroscopy analysis were performed. According to obtained data, the Fe3+ ions were incorporated in the HA lattice, and also amorphous Fe oxides were formed contributed to the gradual increase in the S and pore volume of the powders. The Density Functional Theory calculations supported these findings and revealed Fe3+ inclusion in the crystalline region with the hybridization among Fe-3d and O-2p orbitals and a partly covalent bond formation, whilst the inclusion of Fe oxides assumed crystallinity damage and rather occurred in amorphous regions of HA nanomaterial. In vitro tests based on the MG-63 cell line demonstrated that the introduction of Fe3+ does not cause cytotoxicity and led to the enhanced cytocompatibility of HA.

Phase composition and morphology of nanostructured coatings deposited by laser dispersion of a mixture of polyethylene with iron oxalate

Peculiarities of forming of iron oxide coatings with reinforced carbon nanostructures from gas phase generated by laser dispersion of composite target were explored. Influence of technological modes of heat treatment on morphology and phase composition of nanostructured film layers was determined. It was found that on a substrate highly dispersed layers containing carbon nanostructures are formed. Using Raman spectroscopy it was shown that in oxide matrix carbon structures, which are mainly in the form of planar located nanotubes, appear. It was found that with a mass ratio of polyethylene and iron oxalate equal to 1:1, the distribution of the formed nanostructures in size is unimodal with a maximum near 20 nm. At dispersing of polyethylene and iron oxalate mixture with mass ratio 1:2 in deposited layers nanotubes have the least defectiveness. Patterns of influence on morphology and coatings phase composition of relative component abundance in being dispersed by laser radiation composite target were determined. It was shown that with the growing of iron oxalate concentration in the target coating structural heterogeneity increases, subroughness and average size of separate nanostructures in the deposited condensate grow. The obtained polymer matrix nanocomposite films can be used in sensors.