Tailoring the phase composition and morphology of Bi-doped goethite–hematite nanostructures and their catalytic activity in the degradation of an actual pesticide using a photo-Fenton-like process

The influence of adding bismuth on the phase composition and morphology of goethite–hematite nanostructures was investigated with the aim to develop an active and stable heterogeneous catalyst for the degradation of an actual pesticide with the photo-Fenton-like process. The iron-based nanostructures were prepared by the hydrothermal treatment of solutions containing both iron and bismuth salts precipitated at high pH by two different methods: co-precipitation and separate precipitation. The tailoring of the aspect ratio of the goethite nanorods is achieved by varying the bismuth content in the preparation method. An increase of the Bi content in the reaction induced the crystallization of hematite nanoplates, while the addition of 20% of bismuth salt gives a monodispersed, homogenous mixture of hematite and BiFeO3 nanocrystallites.The degradation of an actual pesticide, containing metalaxyl as the active compound, was studied using the prepared nanostructured materials in a photo-Fenton-like process. It was shown that both the morphology and the phase composition have an important role in the catalytic activity. Samples prepared by the hydrothermal treatment after the co-precipitation showed a higher activity than samples prepared by separate precipitation. Among the samples that contain goethite, the elongated goethite nanorods prepared by co-precipitation with 3.5% Bi showed the highest initial activity, while the best results in the degradation of metalaxyl were obtained in the case of the material prepared with 20% of Bi. The studied catalysts were stable with regard to metal leaching under the conditions employed.

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► Tailoring the iron-based catalysts’ morphology by the addition of Bi to the structure.
► The catalytic activity related to the crystal phases and morphology of the catalysts.
► Homogenous mixture of hematite and BiFeO3 nanoparticles shows the best performance.
► The catalysts were stable in terms of metal leaching under the conditions employed.
► The hydroxyl radicals seem to be produced at the catalyst surface.