Nb-doped hematite: Highly active catalyst for the oxidation of organic dyes in water

•Nb-doped hematite highly active was obtained by the generation of peroxo groups after activation with H2O2.•The mass spectrometry showed that oxidized intermediates were produced.•The niobium introduction into hematite structure decreases strongly the particle size of the material.

The use of iron oxides as materials for advanced oxidation processes has been widely reported, however the hematite phase has been poorly studied. Catalytic cycles show the importance of the redox states of the Fe2+/Fe3+, although hematite has only Fe3+. The introduction of dopant ion, such as 3% niobium in the hematite structure, is able to make it an effective material for treatment of polluted water. In our work it was possible to verify a removal of approximately 45% of a methylene blue (MB) solution (10 mg L−1) using Nb-doped hematite and 75% of the same MB solution using the oxide after a previous treatment with H2O2 to generate surface peroxo groups.

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