Copper-substituted magnetite as a Fenton-like catalyst boosted with electromagnetic heating

Abstract

Copper-substituted magnetite samples Fe3-xCuxO4 (x = 0.0; 0.02; 0.05; 0.1) were synthesized using the co-precipitation method. XRD data revealed that the synthesized samples retain the cubic spinel structure of magnetite. The obtained materials were tested as heterogeneous Fenton catalysts to destroy organic pollutants and inactivate bacteria. The model organic pollutants were oxytetracycline, Congo Red dye, and Methylene Blue dye having neutral, anionic, and cationic nature, respectively. These organic pollutants differ in their adsorption on magnetite surface: oxytetracycline < Congo Red < Methylene Blue. The same order stays for their decomposition rates. The copper-substituted magnetite catalysts also ensure effective inactivation of E.coli bacteria. A contact time of 60 min is sufficient to reduce the number of bacteria by 6-log. In all tests, the catalytic activity of magnetite increases with the increase in Cu content. The maximum catalytic activity was recorded for the Fe2.9Cu0.1O4 sample. Since the copper-substituted magnetite samples are ferromagnetic, they absorb a high-frequency electromagnetic field. Electromagnetic heating results in a significant increase in catalytic activity: the rate constants of the studied catalytic reactions are increased by 1.5–5 times. Thus, copper-doped magnetite is a hetero-Fenton catalyst capable of increasing activity by electromagnetic heating. The adjustable catalytic activity may be useful in water disinfection, where bacterial load varies greatly.