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Mn-substituted magnetite samples Fe3-xMnxO4 (x = 0.0; 0.02; 0.05; 0.1; 0.15; 0.2; 0.25) were synthesized using the co-precipitation method. X-ray diffraction patterns confirmed the formation of pure, well-crystallized manganese ferrite with a cubic spinel structure. The crystallites size increases sharply for the minimum degrees of substitution, with a subsequent tendency to decrease with the growth of manganese ions content. The catalytic properties of Fe3-xMnxO4 were investigated for the degradation of oxytetracycline (ОТС) and inactivate E. coli. There is a correlation between particle size and catalytic activity. The Fe2.95Mn0.05O4 sample exhibited the highest catalytic activity in the destruction of OTC. The effect of electromagnetic heating (EMH) on the catalytic properties of iron oxides were investigated. The Fe2.9Mn0.1O4 sample with electromagnetic heating achieved 100 % efficiency in decomposing 5 mg/L of OTC. Fe3-xMnxO4 samples reduce the number of Gram-negative bacteria E. coli at concentrations of 104 and 106 CFU/mL. Electromagnetic heating experiments demonstrated high performance, achieving inactivation of 6 logs of E. coli in the presence of Fe2.98Mn0.02O4 and Fe2.95Mn0.05O4 catalysts within 135 minutes. Studies on ecotoxicity have shown that Daphnia magna is a sensitive bioindicator of residual H2O2 concentration. An increase in the Mn2+ content in the synthesized catalysts resulted in a decrease in the toxicity of purified water. The study suggests that Mn-substituted magnetite catalysts are effective materials for catalytic decomposition of OTC and inactivation of E. coli bacteria.

The E. coli inactivation using hydrogen peroxide (H2O2) and cobalt ferrite granulated catalyst was investigated in a fixed-bed flow reactor. CoFe2O4 catalyst was synthesized by the co-precipitation method, granulated, and annealed at 1150°C. X-ray diffraction analysis was used to identify the crystal structure of the catalyst. CoFe2O4 catalyst demonstrates good catalytic activity for bacteria inactivation in the presence of H2O2. An increase in the hydrogen peroxide concentration increases the inactivation efficiency. The reactor demonstrates the E. coli inactivation of 99.94% at the H2O2 hydrogen peroxide concentration of 15 mM and initial bacterial concentration of 6·103 CFU/L. The water disinfection using a fixed-bed reactor demonstrates the broad prospects for industrial use.