Brookite TiO2-based materials: Synthesis and photocatalytic performance in oxidation of methyl orange and As(III) in aqueous suspensions

• Brookite TiO2-based materials were synthesized by a hydrothermal method.
• The influence of different experimental variables was studied.
• Pure brookite can be obtained using the appropriate experimental conditions.
• The materials show nanoflower morphology when NaCl is used as sodium ions source.
• The photoactivity was measured by methyl orange degradation and As(III) to As(V) oxidation.

A series of titania samples consisting of pure brookite, brookite/anatase and brookite/layered titanate hybrids were synthesized by a hydrothermal method. The influence of experimental variables, including electrolyte concentration, temperature and duration of hydrothermal treatment, on structural and physical properties of the resulting materials was investigated. The crystalline phase composition of the materials was analyzed by X-ray diffraction, the morphology was examined by scanning electron microscopy (SEM) and the specific surface areas were measured according to the Brunauer–Emmett–Teller method. Pure brookite could be obtained by hydrothermal treatment at 180 °C with addition of 0.25 M NaCl, 0.5 M NaCl or 0.1 M NaOH, and adjustment of reaction time. Brookite samples prepared by addition of NaCl as source of Na+ ions showed a flower-type morphology, whereas those synthesized with NaOH consisted in micrometric-size aggregations of nanoparticles. The photocatalytic activity of the materials was evaluated by means of methyl orange bleaching and by As(III) to As(V) oxidation.

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