The dissertation describes results of studies of the properties of iron oxides and hydroxides of various genesis (biogenic, natural and synthetic), the peculiarities of their phase transformations and their usage. Using the method of electron paramagnetic resonance, the dependence of the magnetic susceptibility of biogenic ferrihydrite from temperature was determined and conclusion about its magnetic ordering was made. The conditions for the formation of a nitrogen-containing radical in hydroxyapatite were determined. Methods for creating of analogues of biogenic iron oxides and hydroxides have been developed, and a number of organo-mineral nano-composites have been created. Using the synthesized nano-composites, “magnetic chain” structures have been created. Using a method of ferromagnetic resonance (FMR), the similarity of properties of the created structures and structures, containing nano-magnetite in living organisms, was proved. It was shown that the parameters of the created "magnetic chains" coincide with the parameters of similar chains of magnetite nanoparticles, contained in magnetotactic bacteria. The effect of "multiresonance" was discovered when magnetically ordered iron oxides absorb electromagnetic waves with a frequency of 9.5 GHz. This effect was observed after thermal treatment of bone samples at temperatures up to 1200 °C. It was shown that after such treatment, rather narrow FMR lines appear. We associate the appearance of narrow lines with the signals from individual ferromagnetic mineral nanoparticles. Similar dependencies were obtained for samples of synthetic nano-magnetite. A probable way of the formation of nano-sized magnetically ordered particles in highly mineralized tissues was proposed. Anomalous dynamic effects, arising under the influence of a strong resonant microwave field in biogenic nano-magnetite samples, were investigated and a model for a qualitative interpretation of the possible mechanism of this effect was proposed. It was shown, that when a strong resonant microwave field is applied to biogenic magnetite nanoparticles, additional signals appear on the contour of the resonance curve, and an increase of microwave power leads to the increase of the number of such signals. That is, a strong resonant microwave field stimulates the transformation of the properties of magnetic particles and turns the system of nanoparticles into a new special coherent state. The phase transformations of weakly magnetic minerals to strongly magnetic minerals in a dry, aqueous and gaseous medium were investigated and explanations of their mechanisms were proposed. The phase transformation of synthetic lepidocrocite with the addition of 4% of starch at a temperature of 600 °C was investigated and it was shown that as a result of this treatment, the magnetite and wustite phases appear, whereas during such treatment of goethite and hematite only magnetite phase is formed. The phase transformations of hematite ore with 2% of activated coal and 4% of starch, at a temperature rising up to 650 °C, were investigated. The reduction of hematite by coal in the temperature range of 400°-650°С leads to obtaining a product with the magnetization of ~ 0.5 A*m2/kg, and only whyle heating to 800 °C the magnetization of the product increases to ~ 10 A*m2/kg. The reduction of hematite to magnetite by starch is completely over already at a temperature of 500 °C. Ideological principles were developed and the equipment was created for the transformation of the structure and magnetic properties of weakly magnetic minerals into strongly magnetic minerals followed by magnetic separation. The high-quality iron ore concentrates were produced from waste iron ore raw materials with the help of created equipment. Phase composition of the samples from the tailings of the «Pivnichna» mining and processing plant was transformed using reducing gases during 60 min at a temperature of 600 ºС. The iron ore concentrate was obtained with the help of the device for the separation of fine-grained iron ore raw materials using the combined impact of permanent and alternative magnetic fields. It was shown that the most complete extraction of iron into the concentrate occurs for finely dispersed technological samples. The highest saturation magnetization (up to 85 A*m2/kg) and the highest concentration of iron (over 69%) were observed for the smallest-grained samples (with a grain size <0.063 mm).
The data obtained can be useful for solving the applied problems associated with the processing of oxidized iron ores of the Krivyi Rih iron ore basin and, thus, solving the environmental problems of Kryvyi Rih region, etc. Among the fundamental problems one should note mineralogical (structure and composition of minerals), material science’s (creation of new materials), technological (creation of high-quality iron ore concentrates) and other problems related to the properties and mechanisms of transformation of iron minerals.
