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The active development of water purification functional materials based on multicomponent spinel ferrites makes it necessary to search for new efficient methods of obtaining initial nanostructured powders. In this study, a two-stage method for the synthesis of perspective pollutant absorption agents based on NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) spinel ferrites are proposed and implemented. The approach is based on the synthesis of the initial powder using the solution combustion method and its subsequent thermal treatment in the air. It was found that synthesized samples are single-phase Ni-Zn ferrites with an average crystallite size of 41.4 to 35.7 nm and a degree of crystallinity of ~95–96%. The analysis of antimicrobial activity against four diverse test-cultures: Escherichia coli ATCC 11229 (non-spore-forming gram-negative), Bacillus cereus ATCC 10702 (spore-forming gram-positive), Staphylococcus citreus NCTC 9379 (non-spore-forming gram-positive), and Candida tropicalis ATCC 750 (yeast) showed that almost all of the synthesized powders exhibit an advanced ability to inhibit the growth of the microorganisms mentioned above. The compositions obtained can be a perspective basis for both natural and wastewater purificators with magnetic separation ability and can find biotechnological and biomedical applications as promising antimicrobial materials.

Nickel-zinc ferrites are important industrial materials in the production of various types of microwave devices; therefore, studies of new methods of obtaining functional ceramic on their basis are of great interest at present. In this work, soft magnetic ceramics based on Ni 0.4 Zn 0.6 Fe 2 O 4 spinel ferrite with low values of the coercive force were successfully obtained under various sintering modes (1000 and 1100 • C, holding time-16 hours) based on nanostructured pre-ceramic ferrite powder synthesized by the solution combustion method. The initial powder and sintered ceramics were investigated by EDX, SEM and PXRD methods. The electromagnetic parameters of the final product were investigated by vibration magnetometry and using the method of rectangular waveguide transmissions in the X-band. It was shown that, depending on the selected sintering mode, it is possible to obtain magnetic ceramics with an average grain size in the range from 1 to 3 µm and with values of the coercive force (Hc) from 16.32 to 19.41 Oe, remanent magnetization (Mr) from 3.39 to 4.31 emu/g and saturation magnetization (Ms) from 67.90 to 78.42 emu/g. After the preparation of a ferrite-polymer composite with different content of Ni 0.4 Zn 0.6 Fe 2 O 4 (0-50 wt%), it was found that the highest absorption characteristics of electromagnetic waves were observed for the sample with 40 wt% of spinel ferrite obtained at 1100 • C, 16 hours sintering mode.

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Nickel ferrite nanopowders were obtained under conditions of solution combustion with the addition of various types of organic fuels (glycine, ascorbic acid, oxalic acid, and malic acid) and studied as photocatalysts in the photodegradation of methylene blue. Photocatalytic measurements were carried out under the action of visible light in model dye solutions. The highest photocatalytic activity was found in the case of a sample synthesized using malic acid as a fuel and in which the largest specific surface area (128.1 m 2 /g) and the smallest particle size (18 nm) were observed. The obtained dependences of the photocatalytic activity of the synthesized samples demonstrate its strong dependence on morphological and structural parameters. Thus, with an increase in the particle size and a decrease in the specific surface area, a decrease in the efficiency of a photocatalyst based on nickel ferrite is observed. In addition, the use of various types of fuels made it possible to obtain aggregates of various shapes and sizes up to several tens of micrometers. The resulting rate constants were established to vary from 0.00756 to 0.00867 min −1 .