Nanoscale Magnetite Research Articles

Magnetic Carrier for Radionuclide Removal from Aqueous Wastes: Parameters Investigated in the Development of Nanoscale Magnetite Based Carbamoyl Methyl Phosphine Oxide

A study on superparamagnetic magnetite polymer composite development was undertaken for application to magnetically assisted chemical separation. Tetramethyl ammonium hydroxide as an alternative to ammonia was used as a precipitation agent to obtain nanoscale magnetite particles. Investigation on stoichiometry control of Fe(III) and Fe(II) ions suggested a correlation between alkalinity and initial Fe(III): Fe(II) ratio for precipitation of magnetite. Studies on polymerization conditions suggested that polymers setting at ambient conditions enable retention of superparamagnetic property of substrate magnetite. Vaporization method for impregnation of solvent extractant CMPO, yielded product that had a high sorption capability for radionuclide europium as compared to wet impregnation method.

Modelling the irreversible response of nanoscale magnetite: Two competing Preisach scenarios

We present a comprehensive experimental characterization of the field and temperature and time dependence of the magnetic response of a powder of nanoscale magnetite particles. The data are analyzed within the framework of the Preisach formalism, and numerical simulations of the field-cooled moment, the zero field-cooled moment, the thermoremanent moment and the isothermal remanent moment, based on two extreme physical scenarios, are compared.

Physical and chemical properties of nanoscale magnetite-based solvent extractant

Nanoscale magnetite bearing magnetic carrier with an adsorbed layer of dibenzo-18-crown-6 was evaluated for removing radionuclides from nuclear waste solutions using magnetically assisted separation method. TEM results indicate that the average size of the base magnetite particles is ∼19 nm. The results of Mössbauer spectroscopy and field cooled (FC) and zero field cooled (ZFC) magnetization confirm the superparamagnetic behaviour of the magnetite particles in the polymer beads at room temperature and hence meet the requirement of magnetic filter regeneration capability.

Definitive identification of magnetite nanoparticles in the abdomen of the honeybee Apis mellifera

The biogenic magnetic properties of the honeybee Apis mellifera were investigated with a view to understanding the bee's physiological response to magnetic fields. The magnetisations of bee abdomens on one hand, and heads and thoraxes on the other hand, were measured separately as functions of temperature and field. Both the antiferromagnetic responses of the ferrihydrite cores of the iron storage protein ferritin, and the ferrimagnetic responses of nanoscale magnetite (Fe3O4) particles, were observed. Relatively large magnetite particles (ca. 30 nm or more), capable of retaining a remanent magnetisation at room temperature, were found in the abdomens, but were absent in the heads and thoraxes. In both samples, more than 98% of the iron atoms were due to ferritin.

Carbon tetrachloride transformation in a model iron-reducing culture: relative kinetics of biotic and abiotic reactions.

Contributions of biotic (cell-mediated) and abiotic (mineral-mediated) reactions to carbon tetrachloride (CT) transformation were studied in a model iron-reducing system that used hydrous ferric oxide (HFO) as the electron acceptor, acetate as the substrate, and Geobacter metallireducens as a representative dissimilative iron-reducing bacteria (DIRB). Over a period of 2-3 weeks, nanoscale magnetite particles, Fe3O4, were consistently formed as a product of iron respiration in this system. CT transformation rates were measured independently in resting cell suspensions of G. metallireducens or in suspensions of washed magnetite particles recovered from spent cultures. Protein and surface area-normalized expressions were derived for the biotic and abiotic reaction rates, respectively. Using the yield of total protein and magnetite surface area formed during growth in the model system as a basis for comparison, the mineral-mediated (abiotic) reaction was estimated to be 60-260-fold faster than the biotic reaction throughout the incubation period. We conclude that G. metallireducens induces CT transformation in this system primarily through the formation of reactive mineral surfaces rather than via co-metabolic mechanisms. The findings indicate that reactive biogenic minerals could play a significant role in the natural attenuation of chlorinated solvents in iron-reducing environments. A novel approach for stimulating reductive transformation of contaminants may be to enhance the formation of reactive biogenic minerals in situ.

Adsorption of Surfactant Dispersed Nanometer Magnetite

Processing of fine particles in a slurry is a difficult problem. Methods to make fine particles magnetic have been developed recently and may offer a solution to this problem. Particles of nonmagnetic materials can be selectively rendered magnetic through surface interactions with magnetic reagents, which are prepared by dispersing nanoscale magnetite (about 10 nm diameter) with surfactants. When adsorption occurs, the magnetic susceptibility of the material is increased. Magnetic enhancement at several orders of magnitude can be achieved. Selectivity of the adsorption can be controlled by the functional groups of magnetic reagents and various surface interaction mechanisms. This approach allows a new degree of freedom for the processing of fine particles, even with conventional magnetic means. Separation and filtration are examples of the applications.